Hey guys! This is technically my second fan fiction (since I decided to publish a Dr. Who story which I am totally NOT pulling a shameless plug for), and it's done for fun & giggles. I hope you enjoy it! Reviews are always welcome. -chaconneviola

"Ever wonder who we'd be if we weren't, y'know, us?" Tony Stark flipped his screwdriver in the air, caught it, and twirled it absent-mindedly.

Across the lab, Bruce Banner raised his head and gave his friend a quizzical look.

"But if I'm not me, who am I?" he quipped.

"Exactly. And Pepper says I'm hard to follow at times." Tony tossed the screwdriver onto the workbench—one of the workbenches—and dusted his hands together. "It's been bugging me ever since the run-in with Evil Spidey."

"Venom," Bruce corrected him.

"Yeah, sure. Same guy, same powers, same… basic charming personality, but you put him in the wrong suit…" Stark shook his head. "An enduring testament to the power of good fashion."

Bruce raised his eyebrows.

"So this is why you upgraded your suit's security. Again."

"I may not be a Boy Scout, but I'm always prepared. Anyway, I happened to run into Reed Richards at the convention last week—y'know, the convention you wouldn't attend—"

"The convention I couldn't attend because General Thaddeus Ross was presenting a—"

"Excuses! You could have taken it down. You need to quit underestimating yourself, big guy. And quit trying to change the subject. I saw Reed Richards at the convention, and you wouldn't guess what he's been working on."

Bruce groaned and kept his eyes on the interface he was re-working.

"He finally got his 'parallel universe' machine working?"

"How'd you know?"

Bruce shot him a quick glance over his shoulder.

"You forget I tried to de-radiate myself while I was on the run. I got fairly close to the fringe and crackpot science community. Even saw your name pop up a few times."

"Was that supposed to be a jab? 'Cause that was pretty pathetic. Wasn't even a poke, really. Yeah, Richards is giving his quantum computer a whirl on Tuesday. I thought…" he shrugged. "We might like to have a look at it?"

Bruce sighed and pinched the bridge of his nose.

"You know how I feel about quantum indeterminacy and casuality."

"Don't think of it as casuality. Think of it as… synchronicity," replied Tony. "Parallel universes aren't necessarily intertwined or even linked."

"They are if you observe them!" Bruce snapped. "Or they become… linked… altered…" He shook his head. "Richards is a brilliant guy, and I have a lot of respect for him. But sometimes there are things you shouldn't mess with. Guess I learned that the hard way." He ended with a self-deprecating laugh.

Tony scowled. He hated it when Bruce made remarks like that—like a stealth put-down, but a put-down to himself. Was that even possible?

"Well, I like to think that every system is worth studying, and every source of data is valuable," he said. "Just think about it. You're a biophysicist—can you imagine getting a few simple cells from a parallel universe? A few molecules? Even a couple loose hydrogen ions. Think about how much we could learn—it's literally the information of the cosmos, and it's just sitting there waiting for someone to come look at it."

Bruce didn't move, just sat there and looked at him with hungry eyes. Inwardly, Tony smirked. Bingo. Get him onboard and make him feel all proud of himself as a genius. Way to go, Stark.

"Well," Bruce said slowly, "it would be… informative… to run a few tests…"

"Informative?" Tony snorted. "It would be the breakthrough of the century."

"Wait, what?"

Both Tony and Bruce turned to see Steve Rogers, holding a half-eaten donut in one hand and looking confused and slightly lost. Behind him, Thor was diligently opening two Pop-Tarts at once.

"What's the breakthrough of the century? A new vaccine or something?" Steve asked.

"Oh…" Bruce said. "It's, um…"

"It's a bit hard to explain, Captain Responsible," Tony said, stepping in front of Bruce and invading Steve's personal space. "Theoretical physics. Parallel universes. Don't think you'd be interested."

Steve crossed his arms and frowned.

"Don't talk down to me, Stark."

"Parallel universes," Thor put in, licking his fingers. "Friend Stark, I am greatly intrigued. Are you venturing into another of Yggdrasil's branches?"

"Uh… branches, sure, let's go with that," Tony said, and opened his mouth to explain further. Unfortunately, Thor did something extraordinary—he cut off Tony Stark.

"Excellent!" he boomed. "I have long desired to show you the nether realms. And you too, Dr. Banner, although I fear you must need your green beast to travel with us on glorious—"

"Uh, no," said Tony, but Thor would not be stopped.

"—Niflheim is wondrous this time of year, and we are sure to meet with hospitality unparalleled by any—except yours, Man of Iron—"

"Uh, no," repeated Tony, wondering why nobody was listening to him.

"—hunting in Jotunheim! And Odin would view it as a personal favor if we put down the yearly Jotunn insurrection; they are worthy foes and will make for glorious battle—"

"Thor, NO!"

Thor stopped, looking slightly hurt. Tony rolled his eyes and sighed.

"Okay, look, we're not going into another realm. It's like… Yggdrasil is a tree connecting the nine realms, right?"

"Of course!"

"Well, this is like… another tree that grew next to Yggdrasil, and the branches are almost touching—see, like this—" Standing on tiptoe, Tony traced a crude diagram of two trees on his digital screen. "There. And we're going to take a peek into the Midgard of the other tree."

"A second Yggdrasil?" Thor looked puzzled. "This is dangerous folly, friend Stark. Heimdall has told me nothing—"

"Thor, just stop," Steve interrupted. Biting his lip, he turned to Bruce. "Is he for real?" he asked, pointing at Tony.

Bruce nodded.

"Okay," Steve said simply. "A… parallel universe. I've taken in floating words, earplug music, and magical food dispensers. I'll deal with a parallel universe when I see it."

Tony glanced up at that.

"Oh. No. Bad. Bad idea. You're not coming. You're not—"

Crowded between Thor and Bruce in the jet, Tony scowled and crossed his arms.

"I hate you, Rogers," he stated.

"So you've said."

"Don't be so hard on him," Natasha said coolly, from the copilot's seat. "He did the nation a great service, alerting us to a new potential threat."

Up in the cockpit, Steve's shoulders straightened a little. Tony ground his teeth together.

"Oh, and that's all that counts, isn't it? An item's value as a potential threat," he sneered.

"Remind me of your business nickname again," said Clint.

"Keep on like that, I'm gonna take back those new arrows, birdie boy," Stark muttered.

"Besides," Bruce put in helpfully, "it really is a good idea to have a pair of military eyes on the experiment. Just in case something goes wrong…"

"I'm going to be doing the experiment; how could it possibly go wrong?" Tony snapped.

Everyone in the jet exchanged glances, but said nothing.

"Did you not fill our dining area with smoke last week?" Thor said. "Twice?"

"Shut up."