A/N: And another prompt fill from avengerkink. I really do love all these delightfully cracky ideas.

Disclaimer: I'm more familiar with MCU than any of the comics-verses, but I am bringing in a few villains that aren't in the movies. If anyone is really familiar with the comics and wants to point out errors, I'll be happy to fix them.

Tony was bored, bored, bored. For the past few days, Bruce hadn't been down to visit him in the lab. Every time Tony asked for his help, it was always some lame excuse.

Like, saying he was still recovering from yesterday's battle. Or that he was going to meet up with some old college friend later than afternoon and didn't have time for any long experiments. Or that it 3 a.m. and he was too tired to start anything now and just wanted to go to bed.

Yeah, that was probably the worst excuse Tony had ever heard.

He couldn't understand why Bruce didn't want to do science with him anymore. What could be more exciting than building things, blowing things up, and catching things on fire?

Okay, so things catching on fire was usually more of an unfortunate accident than a desired result. But, the point being, they were Science Bros. And Science Bros were supposed to do, well, science.

And now Bruce was sitting around in the den with the rest of the team as they read books. Boring.

Tony flopped down into an oversized armchair. "Hey, guys," he said. "Sorry to interrupt your little book club, but I need Bruce to-"

"Busy," Bruce said.

"No, you're not. How can you say you're busy when you're just sitting here-"

Bruce looked up briefly from his book. "I'm busy reading," he said. "I'm allowed to have outside interests, you know."

"Some of us don't live in the lab like you do," Natasha added.

Tony opened his mouth to retort when the doorbell chimed.

"Someone's at the door," he said.

The bell chimed again.

"Isn't anybody going to get that?"

Nobody else said a word, all too busy pretending to be deeply engrossed in their reading.

"Oh, fine, I'll get it," Tony said with a huff.

He marched over to the front door and threw it open. "Hi, welcome to Avengers' Tower. We're not open for tours to the public and no, we don't want whatever it is that you're sell..." he trailed off in open-mouthed shock.

Loki was standing on the porch in full regalia.

"Gah," Tony said. "What the hell are you doing here?"

"Well, this is rather awkward."

"Yeah, I'll say." Tony took a wary step back. "Jarvis, why the fuck didn't you tell me we had a supervillain on our doorstep? Initiate emergency defense systems."

"Wait," Loki said. "I've just come to ask a small favor."

"What, like all of Manhattan on a silver platter? Not fucking happening."

"What's all the shouting for?" Bruce asked, padding up behind him. "Are you yelling at the Girl Scouts again?" He peered around Tony's shoulder and his eyes widened with surprise. "Loki?"

"Dr. Banner," Loki said with a winning smile. "Just the person I wanted to see."

Tony put his arms out. "Hell no. You're not kidnapping him. We've already had to rescue him from fucking Hydra twice this month and I am not in the mood to deal with this shit again."

"Really?" Loki said. "How did Hydra manage this feat? It must have taken a great deal of effort on their part."

"Not really. The first time some Hydra agent at Starbucks drugged his latte and the second time-wait, no, I'm not telling you a damn thing. Get the hell out of here before I have Bruce go Hulk and smash your sorry ass all the way back to Asgard."

Loki took a step back. "Let's not be hasty. I'm not planning on kidnapping him. I just require an article of his clothing. A shirt, perhaps."

Tony raised an eyebrow.

"It's a long story, alright?" Loki said with a heavy sigh. "I started off bragging to my co-conspirators about how easily I turned you all against one another on board your silly ship. And someone expressed doubts about how that was possible when Dr. Banner should have immediately transformed into the Hulk. And then I said that given Dr. Banner's remarkable self-control and my remarkable cunning, of course, it would be possible for me to attack him and escape before there was any hint of the Hulk whatsoever. And now they want me to make good on that boast and bring back an article of Dr. Banner's clothing as proof. But as I am not in the mood for a fight at the moment, I would appreciate it if we could settle this matter civilly."

"Okay," Bruce said. He slid his shirt off over his head.

"Whoa, whoa, whoa," Tony said. He put a hand on Bruce's shoulder. "Bruce, no. We're not giving Loki a single thing. Who knows what he's planning? This could all be a giant ruse to fish for some of your DNA to clone you or something."

"You worry too much," Bruce said. "Jarvis can sterilize it and then there'll be no useful DNA samples left. Right, Jarvis?"

"Of course, Dr. Banner," Jarvis said. "There is equipment down in the lab."

"Great," Bruce said. "I'll be right back."

Tony stayed in the doorway, carefully watching Loki in case he tried anything funny. But Loki seemed perfectly content to wait until Bruce returned.

"Here you are," Bruce said finally. The shirt was now neatly folded and sealed in a plastic bag. Grudgingly, Tony admitted that it was unlikely Loki could use it for any nefarious purpose now.

"Excellent," Loki said. "My reputation will remain intact." He vanished in a cloud of green smoke.

"Okay, that was weird as fuck," Tony said.

"Loki's an odd one," Bruce said with a shrug. "I don't know why you're still surprised that he does strange things." He stuck his hands in his pants pockets and padded back into the den.

"But this was even stranger than usual," Tony protested as he followed after him.

Bruce took his seat back on the couch and gestured to the magazine sitting beside him. "Jane Foster has an article out in Scientific American. If you want to do some reading."

"Ooh," Tony said, eagerly reaching for it.

At last, science.