When the dust settles (literally), the team is back together with everyone that came back after Thanos died, and Thor comes shuffling into Bruce’s lab, head hung.
Bruce had never expected to find a real kinship with any Avenger (at least, not one that wasn’t Tony), but nevertheless there he was, and there Thor was, in his lab and holding something out to him.
“Banner,” he said, “I’m sorry to interrupt your important work, but I have a favor to ask of you.”
Bruce turns around to face his friend— best friend?— with a grin on his face. “Whatever you need,” he says, attempting to ignore the way his heart rate picks up. It’s just because there’s radioactive goop right behind him that he needs to put back into a container quickly.
“Well,” begins Thor, “I found this specimen following me, and I thought it odd.” He holds out his hand, a small rodent of some sort in it. Bright green. “Animals of this sort are not usually not this color, correct?”
Bruce nods his head. “That would be, um, correct.”
Thor’s face lights up. “And I couldn’t help but notice a correlation between this color and the one Loki seems to love so much so I… I was wondering if you have a way to test that this is Loki?”
Bruce feels his expression fall into a smile of pity. “Of course Thor.” He takes the animal and puts it on his desk, beginning to repackage the radioactive goop he knows is important, even if he can’t remember Tony’s reason why. Thor looks at him expectantly until Bruce finally realizes. “Wait, you mean right now?”
Thor’s eyes go wide as he understands his mistake. “No! Of course not, not if you are in the middle of something important. I’m sorry Banner, I—“
Bruce sighs as the last of the goops slides into the container. “It’s okay, Thor,” he says, “let’s do it.” He swabs at the creature with a q-tip and places the cellular extract on a glass plate. Sliding it under the microscope, Bruce looks for any sign of Asgardian DNA. There isn’t any. He looks up at Thor and says “Sorry, buddy.”
Thor’s face falls for a minute before it returns to its usual bright state. “It’s no matter, this is no fault of yours!” He grins largely before continuing. “Loki will return to me in his own time, as he always does.” He turns on his heel and leaves the room, and Bruce falls over looking after him.
Thor walks in again a week later. “I have a frog,” he announces to no one in particular.
Bruce, who is very conveniently the only person in the lab turns around, waiting for more information. When Thor just smiles, he finally asks “And?”
“Would you mind testing this animal for me as well, Banner?” Thor asks.
“Thor, you know frogs are usually green, right?”
Thor battles on. “Yes, well, this one is a very neon shade of green, and I thought it might—“
“Frogs are neon green as well as dark green on earth Thor,” Bruce says, pinching the bridge of his nose. It’s only when he sees Thor’s face drop that he gives in and takes the frog. Thor is right. It is unusually green.
He puts the swab under the microscope, and Thor leans up behind him, invading his personal space. Bruce breathers in sharply when Thor’s head comes to rest over his shoulder. “Well, Banner,” he asks, voice booming, “how goes it?”
Bruce looks at Thor, their faces mere inches apart. Just lean in, the traitorous voice in his head whispers, you’re so close, just lean in.
The third voice in his head joins in agreement with an AAARGH! That one is the Hulk, who, apparently, approves of Thor just as much as Bruce does.
But rather than giving in Bruce lets his head fall as he says, “I’m sorry, Thor.”
It’s not two days later when Thor shuffles in, a green dog tailing slowly behind him. He picks it up and holds it out to Bruce and his face looks like that of the puppy he’s holding and Bruce can’t help but roll his eyes and say “All right…”
So he tests the dog. And there’s no Asgardian DNA.
“You know, Thor,” he suggests, trying to let the god down gently while not ruining any chance he has left, “it could just be a coincidence. Green animals aren’t common, but three of them together doesn’t really mean anything.”
Oddly enough, Thor smiles. “So, you are saying that if there were more than three, it would no longer be a coincidence?”
“Well, yes, but—“ Bruce interrupts himself as Thor’s grin splits open on his face, “wait, why do you ask?”
“Follow me, Banner!” Yells Thor, jovial as ever. Bruce is about to put up a fight, but then Thor puts a hand on his shoulder to guide him and his brain short circuits faster than a battery and a piece of wire. When they arrive at Thor’s quarters (because Avengers HQ is a compound now, not the tower Bruce had remembered) he looks in both directions suspiciously before putting his hand on the wall to open the door.
Inside, Bruce sees what he can only describe as a menagerie. Animals of all kinds, turned green. All the same putrid neon color Loki had been so fond of. There have got to be at least thirty, living, non-humans and non-Asgardians in the room. He turns to Thor stuttering. “See!” says Thor. “Not a coincidence!”
Bruce falls back onto the nearest chair and begins to fan himself. “Banner?” Thor asks, “Banner, are you alright? Sun’s getting real low,” he says, reaching out his hand.
Bruce swats it away, and points to the growing zoo in the corner. “I will test these animals for you,” he says in a tone much angrier than his announcement warrants, “and any other you find, on one condition.”
Thor laughs. “Anything!”
Marry me, Bruce thinks. “You call me Bruce. No more of this Banner nonsense, okay? We’ve known each other for like, a decade now.”
“Okay then…” Thor says, his eyebrows knit together in focus, “Bruce.” Thor smiles at the name.
Bruce is so happy he could die, and then he remembers how many animals he has to test. “Also,” he adds, “Tony can’t find out.”
Thor looks at him solemnly. “You have my word, Bruce.”
Tony, of course, does find out. He breaks into Bruce’s lab one morning at seven, knowing full well Bruce wouldn’t arrive until eight. The back of his whiteboard, the blank side, has several hearts and lighting bolts scribbled on it. Tony is sat on his lab desk when Bruce comes in, and he groans. “Welcome, science bro,” he says, spreading his arms in greeting, “to the science of love.”
“Shut up,” Bruce says, “I’m not in love.”
Tony wiggled his eyebrow suggestively. “The farm animals behind you seem to disagree.”
Bruce looks at the leash he’s holding. A pig, a chicken, and a tabby cat. “Damn,” he mutters, “Old McDonald much, Thor?”
Tony claps his hands together. “Bruce, darling,” he begins, “Welcome to being in love! It’s an awful experience until the other person decides they’re ready to fu—“
“Not in love!” Bruce interjects before Tony can finish his sentence. “And if you don’t mind, I have animals to test for Loki.”
Tony starts laughing. “Step one,” he says, as Bruce tries to get the pig to stay in place, “you need to create a scientifically dangerous situation that will make the person want to kiss you.”
Bruce snorts. “And when exactly has that ever worked?”
Tony scoffs. “That’s how I landed Pepper!”
Bruce mulls it over for a moment. “Yeah, okay I guess.”
“You guess? You guess? Bruce,” Tony says, “In a split second decision I had to find the most romantic rooftop in a ten mile radius where the explosions would appear more romantic than dangerous, and I had to actually save Pepper—“
“Shit,” he mutters under his breath, looking into the eyes of the pig, “Why aren’t you Loki?”
Tony, still ranting about his first kiss with Pepper, didn’t notice Bruce test the chicken and the cat. Still no Loki. When he slammed his fist on the table in frustration, Tony finally snapped out of it. “Woah there, buddy,” he said, “no need to get angry.”
“I’m not—“ says Bruce exasperatedly, “I’m not angry. I’m tired. And Loki’s being a bitch.”
“When isn’t he?” said Tony. “Oh wait, wait. I can do one better.” He took a stern face and pointed an accusing finger at Bruce. In a mock impression of Thor he said, “Watch yourself Banner, that’s your brother-in-law you’re talking about!”
Bruce groaned again, and Tony began to laugh.
Thor kept finding green animals, shockingly. Every day Bruce would show up at his room in the compound and take three more animals to test. Some days Thor would have only have added one green animal to his collection, and some days he would add five.
It was also… nice. It was an ensured ten minutes he could spend with Thor every day. Five minutes of banter when he was picking up the animals, five minutes of comfort after telling Thor that none of them were his brother.
Bruce would have kept it going forever if he could, but his scientist’s mind betrayed him. If there were all these green animals, there had to be a reason for the green animals, right? So Bruce goes hunting, and he finds his reason.
“It’s a rock,” he said to no one in particular, “it’s just a fucking green rock.”
“I don’t know, Banner, I think the past year has proved rocks can be pretty dangerous.”
Bruce leapt about three feet into the air and clutched at his chest. “Jesus Christ, Thor,” he said to the Asgardian behind him, “What did we say about first names?”
Thor grinned, coming up behind Bruce to clap him on the back. “Ah, sorry friend. Old habits.”
Bruce sighed and rolled his eyes. “Sorry buddy,” he said, much more empathetically than he was feeling, “No Loki today.”
“It’s okay! Now tell me about this mysterious rock. What does it do?”
Oh nothing, Thor. It just turns animals green. It’s the reason you think your brother’s alive even though this assures he’s not. Now that I’ve delivered that news, want to make out with me?
“Oh, it’s just been messing with some of my wifi signals in the lab, that’s all. Hey, about how many animals do you have left for us to test?”
Thor smiles “Still a good score!”
Twenty. Okay, he could make this work. “I think I may only be able to test one a day from now on, I’m really sorry about that, is that okay for you?”
Thor laughed. “It is of no matter, for I know one of these days the animal will be my brother! And we shall have a glorious reunion!”
Okay. Bruce had twenty days to break the news to Thor, or to find Loki. He could make this work.
As it turns out, he could not make this work. About three days after he took the rock, Thor had noticed that the green animals he had been finding had petered out, and he looked progressively more upset about it.
It was ruining their ten minutes of guaranteed together time, so Bruce intended to do something about it.
“Tony!” he yelled from across the lab. “How’s that algorithm coming along?” Tony made an indiscernible noise as a response. Bruce sighed. “That’s not an answer!”
After a pause, Tony spoke again. “It would be going faster if you were here, genius! Actually, that’s not a half bad idea!”
“No!” Bruce shouted back. “I’m busy!” But sure enough, that didn’t deter Tony, who came stomping over to his section of the lab, wondering what was keeping Bruce so busy he couldn’t help Tony make the Loki-tracking algorithm he had requested in the first place.
What he had found was Bruce, a bunny, and a paintbrush. The bunny was streaked in green, and struggling. Toy began laughing. “Science of loooove, brother!”
“Shut up, shut up, shut up,” Bruce spat out through gritted teeth. “Don’t you have a job to do or something?”
“Yeah,” said Tony, “but I think I’d much rather watch this.”
When the paint plan, as Bruce has been affectionately calling it, fails, he begins to treasure every bit of his time left with Thor. The logical part of his brain knows that they’ll still live together and that they’ll still be friends, but he can’t help but feel like an era is coming to end.
It’s on the morning of their third to last animal testing that he finds Thor in the lab before he’s opened the door. “Bruce, look!” says Thor, stretching out his palm, “I’ve found Loki!”
Sure enough, there’s a new, green animal. It’s a butterfly, resting gently on Thor’s palm. “Thor, buddy,” Bruce says, realizing that the masquerade is over, “There’s no possible way of knowing that’s Loki until I’ve tested him.”
“Oh,” says Thor, looking puzzled, “I suppose not. I thought the stabbing was a pretty clear sign, though.”
“The what?” asks Bruce, and sure enough the butterfly appears to have driven a small knife straight through Thor’s hand. “Okay, I guess it is Loki then.” He lifted the butterfly gingerly off of Thor’s hand and put it on a petri disk. “Is your hand going to be okay?”
“Yes,” said Thor, beginning to pull at the knife and wincing, “or no. Mind helping me out?” Bruce moved to Thor and placed a comforting hand on his shoulder, squeezing as he removed the blade. When he was done, he could hear the clapping behind him.
“Bravo,” said Loki, back in a human shape, “you’ve cured my brother of his ailments.”
“Loki!” Thor shouted with a wide grin. “You have returned!” He bounded over to his brother in a manner that reminded Bruce of the Labrador retriever he had owned as a child, and enveloped his brother in a hug.
“Ugh,” said Loki, returning the hug immediately, “get off me.” Over Thor’s shoulder he turned to Bruce. “Banner,” he said, “thank you for helping my brother. I’m glad that you’re in love with him.”
“I’m- I’m not in love with him!” Bruce shouted, the tips of his ears turning red. “Why does everyone think that?”
Thor turned around, showcasing his sweetest pout. “You’re not?”
Bruce was the color of a tomato now, which had him wishing he was any shade of the complimentary color. “Well I guess… well… if you want me to be… I guess…”
Loki held a hand up, silencing both of them. “Have this conversation without me,” he announces, “I’m going to find an Avenger to bother.” He stood up and walked out of the room, flipping his coat as he left.
When Bruce turned back around, Thor was right behind him, leaving them staring at each other only inches apart. “Hello, Banner,” Thor says, impossibly quietly.
“Bruce,” he corrects, internally kicking himself for not being smoother.
Thor raises an eyebrow. “Hello, Bruce.”
And that’s it for Bruce, as he grabs the taller man’s collar and pulls, bring Thor’s lips to crash on his own. It’s wonderful, kissing Thor, and Bruce doesn’t ever want to stop. Funnily enough, it seems like Thor doesn’t want to stop either.
When Bruce finally pulls away, Thor lets out a little whine and god if that isn’t incredibly hot. Bruce did that. To a god. “I need to breathe,” he explains, gasping a bit, “not all of us have godly stamina.” Thor, still looking disappointed, nods in understanding before scooping up Bruce to carry him bridal style. “Hey!” Bruce yells in surprise. “What’s your damage?”
“Oh I thought…” said Thor, struggling to find the words, “I would take you to my quarters, if you would find that amendable?”
“Oh,” breathes Bruce, shifting himself to kiss Thor again quickly. “Yeah. Definitely amendable.”
Thor grinned at Bruce, and began to walk. Yeah, Loki may be an asshole, but he was a helpful asshole at least.