It happened while Sheldon and Professor Proton were attending a meeting with the Justice League on Earth One.

Atop the highest spire of the Greater Los Angeles Thinkatorium, Wil Wheaton broke up the fight between Stuart Bloom and Daniel Jackson.

"Sometimes that's how it is," Stuart said. "You start in the middle of the story, you find out what's going on later. It's like a Quentin Tarantino movie. Only without the violence and swear words."

"I'm not sure that's the way to go," Daniel said. "But let's get back to our original topic."

"I'll give you an original topic," Stuart said, raising his fist.

"Guys, guys," Wil chided. "Is this really worth fighting over?"

Both men were gasping and sweating, so much so that Daniel had to slide his glasses up his sweaty nose only to have them slide back down.

"Superman is the best superhero," Daniel insisted in a tired voice.

"Clearly it's Spider-Man," Stuart said in an exhausted voice.

"See how tired you get when you fight?" Wil said.

Extending open palms, one to each man, Wil stood between them like a referee. In fact, he even sported a black-bar shirt for the occasion.

"The best...is Spider-Man," Stuart wheezed.

"Wish I had web shooters like Spidey so I could swing out of here," Wil muttered. Then in a louder voice he addressed his two friends. "Don't you see? You're under the influence of Gorilla Grodd again." The two simply looked puzzled. "Snap out of it!" Wil said sharply while snapping his fingers.

Stuart frowned. "Who are you supposed to be? Snapper Carr?" He referred to a Justice League sidekick known for snapping his fingers.

"I'm your friend trying to get you to stop fighting over nothing," Wil said calmly.

The two men blinked.

"Yeah, okay," Daniel said in his ususal casual-cool voice.

Wil turned to his right. "Stuart, your cover is you run a comic book shop. Does it really make sense for you to argue who's the best superhero?"

Though he had large brown sad eyes, Stuart now looked less puzzled. "No, I suppose not."

"And, Daniel, you're with a team of intergalactic explorers. Don't you have bigger issues to argue about?"

"I suppose I do."

"Okay," Wil said. "Now that that's settled, I need you guys to go fix the Stephanie problem. Like you were supposed to, until you took a ride into the future and started fighting."

"Doctor Stephanie Barnett," Stuart said. "She abruptly disappeared from the lives of our four scientist friends from Pasadena."

"There are a few theories out there as to why," Daniel said.

Stuart nodded. "Some normal, some a little out there."

Wil held up his right hand. "Let's not argue about that right now."

"Wasn't planning on it," Daniel said as he crossed his arms. "It's just interesting that, depending on what dimension you're in, the theory can be true."

STORY ONE: THE E.T. THEORY

"Hello, Stephanie."

Sitting on her aqua blue couch, a surprised Stephanie Barnett spit up wine as she abruptly turned to face the intruders. They were two men, one with a droopy face, the other more normal-looking with normal-looking wire-rimmed glasses.

Immediately, Stephanie chanted in an electronic voice while her blue eyes emitted sparks.

"Intruder alert! Intruder alert!" Her mouth poured out white energy that flashed on and off.

"Easy, Stephanie," the droopy-face man said, holding up an open palm. A device that looked like a gray spider rested on his hand. When it briefly glowed, Stephanie stopped chanting and flashing. "I'm Stuart Bloom, and this is Daniel Jackson."

"Uh, yeah, hi," Daniel said, adjusting his glasses once again. "Not sure how to break this to you." Pausing briefly, he gestured from himself to Stuart. "We're from the future."

Stephanie, understandably, blinked in confusion.

"Am I from the future, too?"

"Actually, you're an alien."

Holding a hand to her head, Stephanie frowned. "An alien? Where am I from? I don't remember."

"There's a reason for that," Daniel said, sounding and looking very authoritative as he stood with arms crossed. "You were given memory loss. As a way to help you cope."

"I would have liked that option," Stuart muttered.

"This isn't about you, Stuart," Daniel said.

"Never is."

Pacing slightly, Stephanie blinked some more. "Yes, it's starting to come back to me. I had to practice primitive medicine. Uck!"

"Yes, there's that," Daniel said. "The thing is, your memory loss didn't always last."

"That's when you would wander off into other realms," Stuart said.

As she took all this in, Stephanie sat on the couch. Her eyes and her face filled with understanding as well as a slight yellow glow.

"That's right. I saw other versions of me. Well, the me I've inhabted. I was in witness protection, I was an F-B-I agent. I was wiped out by time travel. And magic!" Turning, she waved her index finger at the two men. "Penny had magic powers! And Sheldon was the Reverse-Flash!"

"And you're an alien," Stuart said. "Don't worry, though. Once we send you home, we'll wipe out the memory of everyone you knew."

"Everyone in this reality, that is," Daniel said.

Stephanie's blue eyes glowed. "Thanks, guys," she said softly. In an instant, she was sucked up in a vortex of glowing white energy.

STORY TWO: THE WITNESS PROTECTION THEORY

"Stuart, what are we doing out here?"

"We have to make sure Raj and Howard get into the building. After that, I'll quantum-leap into the guy with the gun. Make sure Howard doesn't actually get shot."

"And I'm just supposed to wait out here?"

"Do a crossword puzzle or something," Stuart said in a sharp whisper. "After that, whatever dimension we're in, we just observe."

"Doesn't sound like a fun afternoon."

"Maybe not. But here we go."

"Freeze! Put your hands up!"

A man in a black suit, with a telephone cord near his right ear, pointed a gun at Howard Wolowitz.

"What the frack?" Howard said, nervously raising his hands.

Next to him, Raj Koothrappali wrinkled his eyebrows in a worried look. "Oh, no," he moaned quietly.

Leaning in toward his friend, Howard quietly muttered, "All this because we broke into the house of the Top Models?"

Despite their propensity for hijinks and shenanigans, Howard and Raj were not in a typical situation. At the urging of their friend Penny, they began watching the reality series "America's Next Top Model." Intrigued by the idea of aspiring models living together, they used star patterns and military satellite technology to find the fabled legendary house. That way, they could not only be present for the tickle parties and pillow fights but Howard could find the future Mrs. Wolowitz.

It took them weeks to find the house. During that time, their friend Leonard Hofstadter dated Dr. Stephanie Barnett.

As Raj and Howard carefully searched for the house, Leonard insisted what they were doing was kind of creepy. But once they arrived at the house, Raj and Howard conducted a very gentlemanly break-in. They simply talked to the two women who answered the door.

The one with the short blond hair wore a blue bikini top and a skirt, while the one in front had Britt Robertson type hair while wearing a sleeveless purple mini-skirt. Howard thought the latter looked kind of ditzy.

Instead of expressing that thought, Howard explained they were there to fix the cable.

Further suggesting her ditziness, the long-skirt blonde looked like she was giving deep thought to the matter..

"I think we have satellite," she finally said. She managed to sound sweet even when puzzled. And her voice was kind of ditzy. .

"That's what I meant," Howard demurred.

After brief consideration, Ditzy Blonde lit up. "Okay!" she agreed cheerfully. She swung the door wide open.

Once inside, Howard and Raj began following various models around. While considering his choice for the future Mrs. Wolowitz, Howard thought of the blonde with the short hair. He wondered. What would Penny look like with short hair? And what if she was a sexy pharmaceutical sales rep? Bring on the pills, baby!

Howard often went off on mental tangents like that. But standing in front of the man with the gun, the big scary Secret-Service-type dude, Howard had no more time for tangents.

"Really?" Howard said in a low nervous voice with a slight bow of his head. "You have to pull a gun on me? Excuse me if I wanted to meet some of the Top Models." Here, he lowered his hands just a little. "I'm a romantic," he insisted quietly.

"It's more than that, Howard," someone said.

From a dark area of the room, someone stepped forward. There was just enough light for Howard to recognize...

"Stephanie," Howard said.

Smiling, the woman waved to the man with the gun. "See? We're all right."

"On standby," the man said. He lowered his weapon but did not holster it.

"Hello, Howard," Stephanie said.

This time Howard went on a slightly longer mental tangent. He recalled how he met Dr. Stephanie Barnett one night when he wore an eyepatch to a bar. The red-haired woman with the cheery blue eyes and nice smile looked like a plus-sized model. When Howard offered her a chance to drive a car on Mars, she agreed to take the wheel. Unfortunately, the vehicle crashed.

Howard sent a Code Red to his friends. Sheldon Cooper, a mutual friend to Raj and Howard, was the kind to ask if that was a military hazing, a video game or a Mountain Dew drink. Regrettably, Howard found his friends to be of no help. Raj suggested they call Triple-A even though it would take decades for a spacecraft to reach Mars. Sheldon noted a further obstacle: Howard would need to be next to the vehicle with his card.

Even Leonard wasn't much help. When he took Stephanie home, the two began dating.

Howard attended to the Mars Rover crisis by erasing any evidence anyone had been in the control room. And eventually he stopped pretending Leonard and Stephanie were invisible.

"And now here we are," Howard whispered. Quickly, he realized talking to himself might not be a good idea when there was a guy with a gun. Instead, he addressed his redhead friend.

"Stephanie, what happened? You disappeared from Facebook. The people at the hospital said you were just gone. We've all been pretty worried."

Stephanie responded with a flickering smile. "I'm in witness protection. You don't exactly post that on Facebook."

"I guess not." But then Howard tilted his head back as he made a face. "But why are you hiding in the house of the Top Models?"

"It's only temporary," Stephanie said. "This house actually doubles as an F-B-I safe house. Because no one is supposed to be able to find it," she said pointedly. "But as long as you're here, can you ask Leonard to stop trying to find me and stop talking about me? You do the same, Raj," she said, pointing.

Here, Raj made a shutting-zipper motion over his mouth.

Stephanie turned back to Howard. "I know it might be a challenge, but you'll need to get Sheldon to shut up about me, too."

"That could be difficult," Howard admitted. "I might have to actually hypnotize him."

"Do whatever it takes," Stephanie said.

As Howard held a finger to his chin, Raj whispered, "I'm glad I had some of that alcoholic cough syrup earlier."

Raj carefully watched the guy with the gun while Stephanie talked.

"I remember once I did actually get Sheldon to stop talking. As I told Leonard, I performed a 'Sheldonectomy.'"

As Stephanie giggled, Raj frowned. "Wait a minute. How safe can this place be? We got in."

Stephanie grinned and nodded. "The F-B-I saw you coming. I told them you were okay but they weren't taking any chances."

Raj spread out open palms. "Yet here we are. Took the F-B-I long enough to do something. No offense, dude," he said to the guy with the gun. Then he made a face. "Does he just stand there?"

Howard thought of an episode of "Burn Notice.". There was this bodyguard, a guy in sunglasses and a suit who just sat there, and Michael Westen said he was glad he was not that guy.

"Where's the protection, Stephanie?" Raj asked, a little more shrill than he needed to be.

Stephanie smiled. "Actually, the two women you met at the door are agents."

"Get out!" Raj said. "Well, actually, I guess you shouldn't get out. It could be very unsafe for you."

"Those two were agents? You're kidding," Howard said with a little laugh in his voice.

As the two women entered the room, Stephanie shook her head. "One wrong move, and they would have taken you out."

"Yikes," Howard said.

The blonde with the short hair pulled away part of her skirt to reveal a taser-gun.

"Oh, my," Raj said.

Ditzy Blonde stood with hands on her hips. "So how'd you find this place?" she asked, no longer sounding so ditzy. In fact, Howard found he liked the slightly deeper voice.

"Hey, we're scientists," Raj said glibly with a grin.

Special Agent Very Short Hair had piercing blue eyes that looked deadly serious. "You'll need to come with us," she told Raj in an equally serious tone.

"Okey-dokey," Raj said with a smile. "Bye," he said to Howard.

"Lucky duck," Howard murmured once they were gone.

"So, how did you get in here?" the guy with the gun asked.

Howard bowed his head. "We used military satellite technology," he explained meekly.

Then the words poured out in a great stream. How he crashed the Mars Rover. (Not on a dusty road outside Bakersfield. On Mars!) How while Stephanie and Leonard were at a movie Sheldon walked around making birdlike noises to find the best place for acoustics. In a brief aside, Howard mentioned he loved how Stephanie told that story.

"That's nice," Stephanie said but Howard kept on going.

He talked in a great blur about how Sheldon urged Leonard to open a jar of white asparagus, a way for Leonard to demonstrate his male prowess so he and Stephanie would bond. Instead, Leonard cut his hand, which resulted in several stitches.

"And when I saw the stiches I actually got sick," Howard said, bending forward and almost heaving even as he spoke.

Stephanie smiled sweetly. "Which once again explains why Howard is not a doctor."

Howard looked up at his redhead friend that he had a lot of affection for. "Stephanie, this is so sad. You spent all those years working to become a doctor. Now you have to go into hiding."

Surprisingly, Stephanie smiled some more as she gave a slight shrug. "It might work out all right. Maybe I'll be a receptionist for some old white-haired doctor who could benefit from my expertise."

"Well, I hope things work out for you, even if it's not quite what you expected."

"You, too, Howard." Stephanie's blue eyes looked cheery but moist as she grinned. "I'm sorry things didn't work out with Lisa."

Now it was Howard who shrugged as he assumed a kind of little boy grin. "It wasn't meant to be. I guess it's all right. Sometimes life works out in ways you don't expect."

"I'm sure there's someone out there for you."

"Thanks," Howard said quietly. "And I hope you find someone, too."

Agent Short-Hair and Agent Ditzy Blonde returned with Raj.

"Okay, after talking with Raj here, I'm convinced these guys are harmless," Short-Hair said.

"They could even be helpful," Ditzy Blonde said. "If they can get their other friends to forget about Stephanie."

"You're very kind. And you're such a good listener!" Raj enthused with a big smile.

"You guys are free to go," Ditzy-Blonde said, very authoritative with hands on her hips.

"But don't come back." Short-Hair's piercing blue eyes were even more deadly serious.

"Can't we just keep talking?" Raj pleaded in a groaning voice.

"Sorry, Raj," Ditzy Blonde said with a trace of a grin.

As they all started to leave, Howard turned to his redhead friend. "Have a nice life, Stephanie."

"You, too, Howard."

As the blondes and the guys moved toward the exit, Stephanie called out one last thing.

"Oh, by the way, Howard, I heard the Mars Rover discovered life on Mars. Did you have anything to do with that?"

STORY THREE: THE AGENT THEORY

"So that's the story, guys," Stephanie said. "I'm an undercover agent for the F-B-I. I was only posing as a doctor."

Raj and Howard stood in the house of the Top Models where Stephanie had just finished her story. Both guys needed their jaws lifted.

As a silent invisible observer, Stuart thought that if Amy Farrah Fowler was present, she could say, "Can I close those for you?" Of course, Amy would not arrive in their lives until later. .

Finally, both guys moved their jaws.

"Holy cow," Raj said.

"Yeah," Howard said.

"Now you guys have to go."

As Stephanie waved her hand, the two blond agents began guiding the guys to the exit.

Before they got there, though, Raj's watch played a strange little tune.

That was when Raj's expression suddenly changed. Instead of looking pleasant and agreeable, Raj looked stern, angry, evil.

Moving swiftly, he pulled back Short-Hair's skirt and grabbed the taser, instantly taking her out with a simple tap to the head as he did. He then hurled her in the direction of the guy with the gun. Ditzy Blonde quickly reacted but Raj easily blocked her martial arts blow. Twisting her leg, he hurled her at Stephanie. Moving swiftly, he used his watch to fire lasers at gun guy and Stephanie, taking them both out.

Seeing all this, Howard practically had a panic attack. "Raj, what is this?" he gasped-protested.

Raj didn't even look at him. "Koothrapanties," he said in a bored casual voice.

Howard's eyes glazed over. After blinking a few times, he walked out the exit.

Lifting his wrist, Raj spoke into the watch.

"The package is ready for pickup," he said. Too bad Stephanie saw that League hit, he thought in what remained of his conscious mind.

An image appeared on the watch face: Ra's al Ghul, head of the League of Assassins. With his neatly trimmed dark beard and sinister look, Ra's had some resemblance to the character Ba'al on "Stargate SG-1."

"You have done well, my servant," he said in a British accent, his voice sounding tinny.

"I hear and obey, master. Code word protocol in place."

This referred to the code word Raj uised to hypnotize Howard and wipe out his memory. Unknown to Howard, he had been on several League missions with Raj. Of course, this was unknown to Raj as well.

Years ago, about the time a bored Raj sat in his father's waiting room, he was quietly abducted by members of the League who subjected him to drugs and hypnosis then returned him. Over the years, this happened several times. Through experimental brainwashing methods, Raj was turned into the perfect sleeper agent.

Which raises the question: Why would Ra's al Ghul want someone like Raj, the third son of an itinerant gynecologist, a child born in New Delhi, a boy fascinated with the stars?

Two reasons: It allowed Ra's to use Raj as a guinea pig to explore the effectiveness of various brainwashing techniques. And he wanted a subject that no one would ever suspect of League involvement.

In fact, Ra's even insisted that Raj be programmed with a kind of dorky personality in which the young man liked cooking and colognes and dressing up like a Power Ranger with his friends. Who would ever suspect someone like that of being a League agent?

So it was that Raj stood over an unconscious Stephanie and three FBI agents.

In agent mode, Raj was not always coherent. In fact, he was an odd hybrid of Raj and League agent. Wearing an evil smile, he thought how great it would be if he had a girlfriend who joked about being a serial killer. Then, as the image of Ra's faded away from his watch, Raj thought of a hologram of Princess Leia pleading, "Help me, Obi-Wan Kenobi. You're my only hope."

The watch played its strange tune again, and Raj swtiched from an evil smile to a more amiable agreeable wimpy-yet-lovable look.

"Hey, buddy, wait up," he said as he hurried after Howard.

Abruptly, Howard woke up, gasping and frightened.

Above him, crossed lightsabers cast their green glow.

"That's it," Howard said. "No more late night episodes of 'Arrow.'"

Invisible-observer Stuart turned to Daniel. "Poor guy. He thinks it's just a dream."

STORY FOUR: THE MAGIC THEORY

"Hello, Stephanie."

The blond woman who spoke sounded like she was doing a "Hello, Newman" from "Seinfeld." And her grin held a bit of mystery and malice.

"Uh, hello." Stephanie Barnett briefly looked up as she used the folding platform favored by Leonard's friend Sheldon. A look of recognition followed. "You're Penny, right? You used to live across the hall from Leonard. I remember because one morning you just walked right in. In your underwear."

"Good memory," Penny said as she folded her tan toned arms. That malicious grin was still there. "How's married life with Leonard?"

"It's fine." Stephanie's smile seemed an attempt to hide her obvious discomfort. "What about you? What's new in your life?"

"Funny you should ask. I've been to a little town called Storybrooke. Some nice people there taught me magic."

From behind dark matronly glasses, Stephanie wore a smile that reflected an odd mixture of discomfort and distaste. "Well, your sense of fashion hasn't changed at all." She eyed the bright orange tank top and white shorts with red and blue flowers.

Though Penny had a few lines on her face and her hair in a small tight bun, she looked virtually unchanged from the young waitress who lived in Apt. 4B at 2311 North Los Robles all those years ago.

"Yeah, whatever," Penny said with a trace of snideness. "I've decided I really messed up back then. Leonard's a great guy. And I should be the one married to him."

Stephanie combined a nervous laugh with her fake smile. "I need to go now.": And moved toward the exit.

Blocking her way, Penny held up a thumb and forefinger. "I'm going to make it like you suddenly just stopped existing."

Bobbing her head slightly, Penny snapped her fingers. Stephanie was gone, and in the empty laundry room, Penny watched as images began to form..

Once the images solidified, they flew by rapidly. They were images of past events. From the time Penny first said "hello" to Leonard and Sheldon to all the times Sheldon knocked on her door. And a few times when she knocked on his.

There were brief images of Leonard going out with Stephanie. After Stephanie announced on Facebook she was in a relationship with Leonard Hofstadter, Leonard and the guys all suddenly went blank. No more memories of Stephanie.

"Ha!" Penny said. "Even you can't fight magic, Sheldon!"

As the images showed a new timeline, Penny waved her hand, causing those images to fly by even more rapidly. Then a stop, rewind. Leonard was down on one knee holding out a ring.

"Penny," he said. "Will you marry me?"

"Yes!" Penny shouted as she watched herself accept. "Yes, yes!" she shouted as she ran in place. As she hugged herself, she could almost hear an audience cheering.

Of course now that she, not Stephanie, was married to Leonard, she would have to keep her powers a secret.

But now there was a whole new future ahead.

STORY FIVE: THE TIME TRAVEL THEORY

"This is what happens when you just go for a ride in your time machine," Leonard Hofstadter grumbled from the driver's seat.

"Told you we shouldn't have been spontaneous." Next to Leonard, Sheldon Cooper spoke in a low quiet voice. "Spontaneity should always be planned."

"Thank you, Sheldon."

Sheldon pointed to a device on the control panel, which was modeled to look like Doc Brown's console from "Back To The Future."

"You should have used the G-P-S."

"It's not a G-P-S. The 'G' stands for 'global.' How can a G-P-S tell us where we are globally when we're traveling through time?" Leonard's voice took on a tone of increasing frustration until he sharply punctuated the word "time."

"That's what we call it," Sheldon said calmly. "When you're doing something unfamiliar, it helps to call things by a familiar name."

Leonard found it interesting that his roommate-friend-colleague/time-travel-lab-partner suddenly stopped being such a literalist. But Sheldon's comments did show how he liked things to be familiar and routine. Some might call that obsessive-compulsive. Or insane.

"Better get out and see what we did," Leonard said in a mild groaning voice.

Lifting the silver door, Leonard stepped out. The time machine looked like a cross between a DeLorean and the Jetsons' flying car. In the back was a round red wheel, modeled after the one from the time machine in the movie "The Time Machine." As it turned out, such a wheel was essential to navigate the time currents.

"Oh, great," Leonard groaned. "We hit someone. I'll consult Ziggy."

Leonard pulled out what looked like a misshapen Rubik's cube, one in the form of a cross. On time jaunts, Sheldon could play with the handheld device like it was a Rubik's cube, albeit one with flashing colored cubes and R2-D2 noises. Oddly, this did not get him wound up. But looking out the window did.

On a journey through time, one could look out the window and watch the events of history fly by at incredible speed. It was like watching a DVR on really high fast-forward. Leonard could look out the window and be fine. But when Sheldon did it, he started acting like he'd just had a huge dose of caffeine.

Thankfully, there was an alternative. Sheldon's brain could be hooked up to the Interactor. This allowed him to play the text game "Zork" while also playing Words With Friends with a simulated Stephen Hawking (who, years ago, had gone completely artificial intelligence). Sheldon could do both those things while also watching "Star Wars." And there were lots of activity books in the backseat.

"It's taking Ziggy a while," Leonard said, bouncing on his toes like a nervous little boy.

"As usual," Sheldon murmured. "I'm glad it's Ziggy the computer program and not Ziggy the comic strip. That thing is full of holes."

"You know, Sheldon, we could have avoided all this if instead of building a time machine, we quantum-leaped."

In a kind of mild double-take, Sheldon made slight back-and-forth movements of his head. "Oh, Leonard, you know I don't like the idea of borrowing someone else's body. Besides, how would we leap together?"

Under his Clark Kent glasses, Leonard directed his dark eyes up at his tall friend. "Doctor Beckett and Al do it," he said with a slight shrug.

"Al arrives after Doctor Beckett. And sometimes Al has trouble finding Doctor Beckett." In his white jacket with tan squares, Sheldon looked remarkably unperturbed.

"You know, Sheldon, you seem very calm, especially considering we've just been in a car accident."

"Technically, we were in a car-and-time-machine accident. It's no big deal. We'll just exchange insurance information."

"Right, Sheldon. And they can wait how many years before they collect?" When the handheld device at Leonard's side sang, he lifted it and read the info. "Oh, my Grat! It's Roger and Linda Barnett. Stephanie's parents! I remember them now from that picture at Disneyland! We've probably caused Stephanie not to be born!" Ziggy made a loud noise. A wheezing-squealing-cry-of-surprise noise. "We have caused Stephanie not to be born! Sheldon, quick! Get out a Post-It Tablet!"

Sheldon ran his hands all over his tan and white jacket.

"Come on, Sheldon. You know the drill. We only have a few seconds before Ziggy loses all the data about Stephanie and we lose our memories of her."

"Trying," Sheldon said.

"Sheldon, you have interdimensional storage pockets. You have everything in there."

"I must have lost the key-code-opener when we crashed."

"Sheldon, we're going to forget any second now!"

"I know!" Sheldon said in a frantic gasping voice. As he ran in place, he continued running hands over his jacket.

"Hurry, Sheldon, before we forget!"

Suddenly standing still, Sheldon blinked. "Forget what?"

Leonard made a face. "I didn't say anything." He turned his head. "Huh. Look at that. Those people must have run off the road."

Sheldon looked at the silver Impala with the dent in its rear bumper. "I'm sure it's of no historical significance. These people probably weren't that important."

"Probably not," Leonard said. "And we really shouldn't interfere in the events of the past."

"Obviously."

As Leonard placed Ziggy back on his utility belt, the handheld device squealed then made brief R2-D2 noises.

"So, where should we go next?" Leonard asked as they got back in the DeLorean/time machine.

"Take us to our default point in time."

While Leonard pushed the default button, Sheldon put on his interactive helmet, which made him look like Robocop.

As the events of history flew by outside the window, Leonard said, "You know, Sheldon, maybe we should have thought this through a little bit more. What if the time machine gets damaged? How do we fix it? We can't take it to a repair shop. And you and I aren't exactly mechanical experts."

"If 'Back to the Future Part Three' teaches us anything, it's the dangers of a time machine breakdown." Still looking like Robocop, Sheldon turned and addressed his friend. "Should the time machine break down, we just wait a number of years until we can repair it. Then once it's repaired we go back and tell ourselves how to do it."

With a puzzled/concerned look, Leonard glanced at him. "Do you really think you have the patience for that?"

As Sheldon paused briefly, the lower part of his face showed a slight frown. Then: "I hadn't thought of that."

"And what if we don't live long enough for it to get fixed?"

"Good point," Sheldon said. A moment of consideration. "I suggest we limit our time travel trips to the future, just as we have been doing up until now. In the future, they're more advanced."

"Good idea," Leonard said.

After a few seconds, a slight hum indicated the time machine was decelerating. The default setting had brought them to March 13, 2024. The time machine landed with a slight "whoosh" followed by the sound of a balloon slowly leaking air.

They were at their apartment building at 2311 North Los Robles in Pasadena. Outside that building stood a lone figure: Stuart Bloom, owner of a comic book conglomerate. Naturally,Stuart looked slightly older from when the two last knew him in 2018.

Of course they hadn't seen much of him. Over the years, the guy was always rushing around doing something, it seemed. But here he was now standing perfectly still for a change. With a few lines on his forehead, he had the same droopy face while his big sad brown eyes were under wire-rimmed glasses.

"Hey, guys," Stuart said. "Nice ride."

"Hey, Stuart." Leonard thought it strange Stuart seemed only slightly surprised by their time machin. "What are you doing here?"

Stuart's head bobbed a little as he spoke. "A bunch of us agreed to meet here on this date." With a glum look, he glanced around. "Looks like I'm the only one who showed up. Well, except you, of course, Leonard."

Leonard made a face. "I don't remember anything like that. I'm just here by coincidence."

"Is anything by coincidence?" Stuart asked.

"Uh, yeah," Leonard said.

"I should probably go," Stuart said.

"Or you could be time travelers with us," Leonard offered with a smile.

"Beats standing here," Stuart said.

Once Stuart was in the back seat, the guys set on their way.

"Hey, Sheldon, guess where we're going?"

"I never guess. I draw conclusions based on observation."

"Remember when I signed that part of the Roommate Agreement about time travel?"

"I remember everything," Sheldon said, still under the helmet.

"Not everything," Stuart muttered from the back seat.

"And you didn't sign it, you initialed it," Sheldon said. "It involved how if either of us invents time travel we would show up five seconds after that moment."

"Yes!" Leonard responded cheerfully. "That's where we're going!"

"Oh, Leonard, we can't do that."

Leonard's smile started to fade. "Why not? We'll save ourselves a lot of time. No pun intended."

As he often did, Sheldon ignored the joke. Or more likely missed it altogether. "Leonard, if we go back to that moment, we might set off a chain of events where we change all kinds of things in the timeline. And not for the better." With the helmet rattling slightly, Sheldon shook his head. "Honestly, Leonard, have I taught you nothing?"

"Apparently not," Leonard said in his holding-my-tongue voice. "But I say we should do it anyway. Just to see what happens. We can always fix it later."

"You might not end up with Penny," Sheldon said.

"Let's go somewhere else," Leonard decided.

"Excellent thinking," Sheldon said with a grin. "Now that that's settled, I have a much better destination in mind. But first we'll have to let the G-P-S recalculate." After pushing a button on the console, a slight whining noise indicated the GPS was powering up.

Sheldon turned to their passenger. "Stuart, do you know one of the best things about time travel?"

"I don't know. Hot babes in the future?"

"Stuart, be serious."

A blinking Stuart shrugged. "I suppose there's a lot of great things about time travel."

"Yes, true, but this relates specifically to you." Sheldon grinned some more as he continued in a cordial pleasant tone. "I can buy a brand new comic book today—'today' being a relative term in time travel, you understand—I can buy a comic book, take it into the future and sell it in mint condition for hundreds of thousands of dollars." He emitted his distinctive gasping laugh.

"What an interesting idea," Stuart said with a nervous chuckle.

"We've financed a lot of our time travel trips that way," Leonard said with a smile.

"So have I," Stuart mumbled.

"What's that, Stuart?"

"Nothing." Stuart wondered why the activity books next to him felt so lumpy, solid and warm. And was the time machine making a noise that sounded like snoring?

"We obtain money in the current currency of whatever time we're going to," Sheldon said with a grin. "Just like Doc Brown did in 'Back to the Future.'"

"In one time period, they switched from gold to silver," Leonard said.

"Just like in that 'Twilight Zone' episode."

"I think that's where they got the idea. They were big on the 'Twilight Zone.'" Leonard spoke in a laughing cheerful voice. "Anyway, we bought a lot of silver from our time. Real cheap."

"I've opened bank accounts for different periods in the future," Sheldon said with more of a grin. "The interest really adds up."

"That's the thing to do," Stuart said. "Always be prepared when you're traveling around."

Here, the voice of Sheldon came out of the GPS. "Let's go on a trip to an exciting future. Here are your directions. First, slingshot around the sun, go to the thirty-first century and take a sharp left at the Rock of Eternity."

"Oh!" Sheldon exclaimed. "Sounds like that fellow knows what he's talking about. Leonard, be careful not to turn into an alternate dimension."

"You are not going to let that go, are you?"

Following the directions, Leonard brought his passengers to a domed city with tall spires and flashing lights. It looked like the art director for "Batman" had gone nuts.

Again, Leonard spoke in a laughing voice. "Whoa! What is all this?"

Sheldon-on-GPS answered. "Welcome to the year Seventy-Ten. Here you'll find cybernetic helper-monkeys and the playful dog-apus. Best of all, a Thinkatorium with telepathically-controlled flying dolphins." Sheldon's signature gasping laugh followed.

"Wow!" Leonard said with his biggest smile yet. "It's all here. Just like you said, Sheldon."

Sheldon's voice became a little deeper. "There's a reason for that, Leonard. You see, I'm from the future."

"You're what?" Leonard said.

"Yeah, what?" from Stuart.

"I'm from the future," Sheldon repeated calmly. "Not an alien like Penny always thought." He shook his head. "Penny always got things wrong."

"What?" Leonard said.

"Yeah, what?" from Stuart.

Removing the helmet, Sheldon sat with hands on hips. "You see, gentlemen-" Here, Sheldon's voice took on a loud eerie reverberating tone. "-I am the Reverse-Flash!"

"Didn't see that coming," Stuart mumbled.

"Me, either," Leonard said.

"Wait a minute," Stuart said. "This explains why Sheldon was always so obsessed with the Flash."

"Yes, Stuart." Sheldon spoke in a voice that sounded like he was vibrating. "As I traveled back in time, I ended up on your world. A world where the Flash is only a comic book character. Regrettably, my super-speed ran out and I've been trapped in your primitive time period ever since. But through comic books I've been able to gather plenty of intelligence about the Flash."

"Huh," Leonard said. "You don't say. How about that? Well, I always knew you were unusual."

Stuart gave Leonard a light tap. "Hey, how about that, Leonard? You always said Sheldon was one lab accident away from being a super-villain. But he already was one."

"And I needed the time machine to make several test runs into the future before I could be sure I would make it home," Sheldon said. "But here I am, in my home. The future. Because I'm from the future."

"I'm from the future, too," someone said, rising suddenly from the pile of activity books in the back seat.

"Doctor Daniel Jackson from 'Stargate S-G-One?' Yay!" Sheldon exclaimed.

"Hey, guys," Daniel said.

"Well, I have a busy day," Sheldon said as he opened the door. "I have to get my super-speed back then get on my Cosmic Treadmill and confront the Flash. Farewell, gentlemen." Leaping out of the flying time machine, Sheldon began flying around in jet boots.

After watching Sheldon fly around for a little while, Leonard turned to his newest passenger. "Wow! Daniel Jackson? For real?"

"I'm real," Daniel said in a sleepy voice. "Last time you guys visited the future I stowed away and fell asleep back here. But I am from the future," he said as he yawned..

Leonard made a face. "Am I the only one here not from the future?"

"Looks that way," Daniel said.

"So we meet again, my old enemy!" Stuart shouted. He quickly removed his glasses and coat to reveal a perfectly sculpted physique in a bright blue and yellow costume. The two men took off flying in their own jet boots and wrestled in the air far above the domed city.

The time machine's onboard DVD player displayed a scene from "Smallville" where Clark Kent and Lex Luthor wrestled in the air. Sheldon had programmed the DVD player to respond to outside stimuli and visual cues and then display appropriate video clips.

"Yep, I'm the only one not from the future," Leonard muttered. He used the time machine to return to his own time where in an unusual arrangement. Howard, Bernadette, and Amy raised his three test tube babies while Penny was off in Hollywood. Thanks to a special pill, Penny was able to be an actress, pharmaceutical sales rep and superheroine all at once.

"Hello, Flash." The man spoke in a voice more snide than menacing.

"Uh, hello." Barry Allen a.k.a. "The Flash" looked more confused than concerned. The tall lanky man, who looked like a giant praying mantis, wore a black T-shirt with the Flash lightning bolt symbol. Was he part of some weird fan club? Or another meta-human?

The praying mantis man pointed a finger and in his face was an air of superiority.

"If you don't do exactly what I say, I shall kidnap your wife Iris."

Barry/the Flash made a face. "My wife? Iris isn't my wife. We're not even dating."

Praying-mantis man looked confused. "You're not?"

"No, she's going out with Eddie Thawne."

The man looked even more confused. "That can't be right. I'll need to consult Ziggy."

"Ziggy?"

Sheldon turned away from his opponent and punched several buttons on his handheld device, causing the device to emit a series of small squeal-sighs. Behind him were the sounds of fists beating rapidly.

"Save your energy, Flash. It's a force field even you can't penetrate," Sheldon said in a bored voice. Then a more irritated tone. "Stop making all that noise! I can't concentrate!" He slapped the side of Ziggy, who responded with a squealing scream. After he read the info, Sheldon said, "Oh, I see. I have the wrong world. My apologies. Carry on."

Returning to his Cosmic Treadmill, Sheldon went to the dimension he called "Flash-World." Here, the Flash was more like the one he had been reading about in recent comic books.

But when Sheldon materialized in the bustling downtown district of Central City, he saw a familiar grinning bearded man looking directly at him.

"Hello, Sheldon," the man said cordially.

"Wil Wheaton! What are you doing here?"

The two drew closer to keep passersby from crossing in front of them. As they did, Wil explained.

"Like my counterpart Wesley Crusher, I travel to other realms to help fix problems. Kind of an inter-dimensional 'Kung Fu'/'Fugitive'/'Incredible Hulk.'"

Sheldon did that thing where he gasps and lights up at the same time. "Do you actually turn big and green?"

"Not actually, no."

"Oh," Sheldon said as he briefly drooped. Then he stoood up straight as he grinned. "I don't actually help fix problems myself. Instead, I create problems."

"I can believe that."

"Actually, I just really try to destroy the Flash."

Holding up a finger, Wil stepped even closer. "That's kind of what I wanted to talk to you about. Sheldon, why do you want to destroy the Flash?"

Sheldon did a mild double-take. "Why, Wil, it's what I do. I'm the Reverse-Flash."

"Have you thought of doing something else?"

"Like what?"

"You like superheroes, right? Have you thought of joining a superhero team?"

"I do like superheroes." As he thought for a moment, Sheldon grinned. "And during my time on World B I learned to like paintball and Thai food and tiny Spock action figures."

"You could be a superhero and still enjoy all those things and more. You'd just have to, you know, stop trying to destroy the Flash."

"Trying to destroy the Flash does take up a lot of my time," Sheldon admitted. "And what do I really get out of it? I don't get money or respect or friends. Being a superhero might work a lot better. You know what, Wil? I'll do that instead!" Sheldon emitted his gasping laugh.

"Glad to hear it," Wil said, giving him a light tap on his lanky arm. "Now if you'll excuse me Professor Proton and I have other realms to travel to."

Sheldon did another mild double-take. "Professor Proton?"

"Yes, he's a superhero on another world. Uses accelerated science experiments to fight crime."

Behind Wil, a figure stepped out of a portal. Dressed in bright red, Professor Proton offered a faltering smile.

"H-Hello, Sheldon. H-how you doin'?"

"Oh, this is wonderful!" Sheldon exclaimed. "Wait. I have an idea. I'll travel with you to other realms while I look for a superhero team."

A worried-looking Proton turned to Wil. "L-let's find a team quick," he stammered.

Wil nodded. "I'll drop you guys off with the Justice League on Earth One then I've got some other business to take care of."

"Oh, goody! I can join the Justice League for real!" Sheldon pulled out his Justice League membership card as all three men were engulfed by a portal.

EPILOGUE: STUART AND DANIEL

After fighting each other above the Thinkatorium in 7010 where they encountered Wil Wheaton, Stuart and Daniel visited several dimensions to see how Stephanie disappeared. After that, the two went to Stuart's comic book shop on Prime Earth Two.

Accompanied by squishing and slurping sounds, Stuart assumed his younger non-superhero form. But he noticed Daniel looked mildly grossed out. Stuart shook his head. For all of Daniel's talk about how all lifeforms had rights, no matter how weird they looked, the guy could be kind of a bigot.

"So," Stuart said. "As always I'll stay on here as an observer. I can make sure the Sheldon of this realm doesn't regain any memories of Stephanie."

"That could happen," Daniel said. "The Sheldon of this reality is slightly out of phase with this realm."

"Most Sheldons are," Stuart said. "But don't worry. If I see any signs that Sheldon is regaining his memory, I'll give him another zap." He held out a fist with a plastic Green Lantern ring and the silver-spider device.

With his thumb, Daniel gestured to the exit. "I'll just head back to S-G-One."

Leaning in, Stuart spoke in a low sing-song voice. "Don't tell them you're from the future."

"I think I know that."

Stuart's head shot back. "Whoa! And I thought Colonel O-Neill was the snarky one." He offered his Green Lantern fist. "Keep things on course, Daniel."

Daniel gave him a fist bump. "You, too, Stuart."

Once Daniel was gone, Stuart leaned on the counter and sighed. But then there was the slight trace of a grin.

Ha! he thought. Doctor Who's got nothing on me.

EPILOGUE: THE WRITERS ON ANOTHER WORLD

The writers of "The Big Bang Theory" (on Earth Prime, that is) gathered in the Writers' Room.

"Couldn't we write just one line explaining what happened to Stephanie?" one writer asked.

"I don't think we have time," the head writer said. "We just have so many other ideas to work on."