I do not own the Big Bang Theory, and am merely putting a story that I've been wanting them to approach for a long time. This will be a multi-part story. And I hope you enjoy...-LongLoreLover

The Evil Twin Prognosis

Leonard walks into the living room, and sees Sheldon working on his whiteboard. Sheldon's back is to Leonard, and Leonard's face lights up with an evil smile. He starts forward, creeping quietly, and when five feet near Sheldon...Sheldon without turning says, "Back right up soldier!"
Leonard is confused as he really looks at Sheldon. The lanky physicist is wearing a black suit, his hair slicked back, and his hands holding the marker with extraordinary precision.
"Sheldon, are you alright?"
Sheldon tugs at his shoulders and says in a smooth voice, "But of course Leonard. How was your REM sleep?"
"...Fine."
"That is good to hear my good but short man."Sheldon went back to his work, and Leonard seriously considered he was dreaming. Sheldon did not talk like that, and never wore a completely black suit, although there was that one time when he got drunk...
A knock on the door rouses Leonard, but Sheldon moves to it, moonwalking on the way and humming "Smooth Criminal" by Michael Jackson. Leonard stares hard at Sheldon, cleaning his glasses.
"Since when do you MoonWalk?" he asked, and Sheldon winked, "Stay tuned my good man."
Leonard decided that he needed to wake up and scrunched his eyes. As Sheldon opened the door he said, "Leonard I'm not sure if you're thinking but if you aren't then please don't defecate on the floor."
The door opened, and Amy Farrah Fowler stepped in. "Good morning Shel-"she stopped and looked at the man who was standing in front of her.
"You're not Sheldon."
"That's what I was thinking." Leonard pitched in, and Sheldon shrugged. "But I am Sheldon..."
Amy ran to Penny's door knocking hard three times.
"Penny Penny Penny!"she repeated, and Penny finally opened the door. She was wearing her light blue robe, and had that sleepy look on her face.
"Hi Amy. What do you need?" Penny asked. Amy slapped Penny in the face, causing Penny to scream in pain.
"Am I awake!" Amy asked, and Penny replied, "No but I sure am. Ow!"
Amy grabbed Penny by the arm and pulled her into Leonard's apartment, snapping a finger at Sheldon, who began to say, "It's not nice to point fingers at peo-"
"You be quiet!"Amy shouted, and Sheldon raised his hands in mock compliance. "Penny, is that Sheldon?" Penny gave Sheldon a long look, in which Sheldon said, "Well since we are all here, I will say that I am not Sheldon."
"Aha!" Amy shouted, and then she looked to Penny, "I knew it."
"Then why the hell did you have to hit me in the face?"
"A scientist always double-checks hypotheses before submitting them to the public..."The fake Sheldon echoed.
Leonard gave him a look and said, "You're a scientist?"
"That would be precise Leonard, although my field is a little more complex."
It is at that point that the real Sheldon came out of his room and stood in the hallway.
"Good day a-"Sheldon stopped when he saw his suited-up counterpart.
"What are you doing here?" He demanded, and Fake Sheldon dryly said, "Nice to see you too bro!"
"Bro?"Leonard, Penny, and Amy asked. Fake Sheldon was about to explain when he raised his finger and said, "We have company."
They turned to the door and saw nothing. "You're just as crazy as-"Leonard was interrupted as Raj came through the door.
"Greetings white people!" Raj said, and then stopped as he laid eyes on the Two Sheldons.
"Howard get in here!"
"Raj we acted this out already. Now bring them to me..."Howard said from out in the stairway.
"Howard get your skinny buttocks in here!" Raj demanded, and Howard sighed before coming in. Both were wearing identical red and white stripe jeans with black muscle shirts; that didn't really show that much muscle.
Howard gasped. "Good God he succeeded in cloning himself..."
"Excuse me, but I am nothing like that inferior model." Fake Sheldon said, pointing to the Sheldon near the bathroom, who said, "Well this model is way better looking."
"What are you theorizing we're identical!" Fake Sheldon said to real Sheldon, who made an annoyed face.
"Forgive that one, he was never good at replying to humor, and frankly I think that's one of the few subjects he never passed."
"They have a class on humor?"Penny asked.
"Yes. Life."Fake Sheldon said. "Well now that everyone is here, I shall introduce myself. My name is Leo."

"Oh cool, you have the same name as Sheldon's cousin!"Penny exclaimed, and Leonard, Sheldon, Raj, and Howard shared a mortified look. A few years ago, Leonard lied to Penny about going to a symposium in order to avoid hearing her sing. Sheldon, who became unhappy with the simpleness of the lie, morphed it into an ununravelable web of lies that consisted around a fake cousin Leopold, who was dealing with substance abuse. Penny never found out Leopold was a lie, since Sheldon had hired an actor to portray Leopold. (And now back to the story)

Leo gave Penny an unknowing smirk, tilting his head towards Penny. "My good girl, Sheldon does not have a cousin Leopold. I should know I'm his brother." That drove all other Leopold questions away. Sheldon strode into the kitchen and got some Big Bran from the top of the fridge. Everyone else in the meantime was looking at Leo, who was clearly enjoying all the attention.

"You're Sheldon's brother!" Howard asked in disbelief, and Leo nodded to him. "Indeed, we are identical twins." Another bombshell. Penny waved her hands and said, "Wait wait wait. Which one of you is smarter?"

Leo laughed and said, "That would be me." Howard had a brief flashback of how he use to say that line. It made him smile. Sheldon however said, "Not likely. Leo here is a gigolo."

Leonard looked at Leo,. "Really?"

"Yes." Sheldon said before coming over. It was at that moment that he realized Leo was in his "spot". Everyone held their breath as they waited. "You're in my spot."Sheldon finally said, and Leo for once looked exasperated.

"You've got to be kidding me Shelly! You did this at the house too!"

"Leonard he's in my spot."Sheldon said, and Leonard tried damage control.
"Yeah Leo just get out. He has this thing-"
"With strikes and three strikes and you're banished? He made you sign a Roommate Agreement didn't he?"
Everyone stared at Leo. "How do you know that Leo?" Amy asked, and Leo smiled. "He did this same crazy stuff back at home.-"
"Excuse me but I'm not crazy you of all people should know this mother had me-"
"Tested I know but I always said those machines were bogus!"
"You're still in my spot. Get out."Sheldon argued, and Leo smiled.
"I think not Shelly. After all, I'm you in a much better form and figure, so I have the right to your spot too."
Sheldon stared at his brother for a long time. "That's it you're banished goodbye."
"What?"
"Spring 1196 you were at two strikes. This makes three."
"Yes but they get erased from your record after one year. It's been 16 since then. I have a clean slate."
Sheldon's eye twitched. "One strike two strike..."Leo got up, dusting off his pants.
Sheldon smiled, sat down, and then scowled.
"What is it Sheldon?" Leo asked innocently.
"You and your outrageous perfume!"Sheldon accused while sneezing profusely. Penny sniffed and said, "I don't smell anything."
"But of course not my dear. This perfume is sensitive only to Sheldon."
Everyone looked at Leo. "Can we have some?" they all pleaded, and Leo laughed.
"He is awful is he not?"he chastised while Sheldon left. He shot a glare at Leo and said, "I hate you."
"Well at least I have no panties for you to string up..."Penny looked at Leo in disbelief and he only said, "I have my ways."
Amy sat right next to Leo. "Tell me about yourself Leo."she said seductively.
Leo got back in Sheldon's spot, and looked at Amy Farrah Fowler. "I think I will pretty Miss."He raised his hand and started, "It was a bad drought in Texas..."