You know? I never watched Adventure Time as much as I should have, but MutliVersus being back made me realize that, while he would try to be respectful, Finn's princess-kink having ass would take ONE look at Wonder Woman, scream "GYAAAAATT!!!" at the top of his lungs, and explode on the spot. Like, straight up spontaneously combust.
That, or he'd INSTANTLY crush on Arya and get DEMOLISHED before he can get a word out.
I'd also find it funny if they actually do hit it off and become friends because Arya doesn't really get to be goofy anymore and then he introduces her to Jake (who she refers to as "Gloopy Dog" still) and explains how he's more a brother than a pet.
Arya then mentions she had a pet too, but that she had to send her away to save her life, and they only saw each other once afterwards. Shame too, she was a WONDERFUL and adorable little puppy and she loved her very much. The sweetest thing, really...
Finn is IMMEDIATELY distraught, and, Finn and Jake being Finn and Jake, propose that "Hey! Where in the Multiverse! Maybe she's around! Try calling her!" and Arya waves it off at first, but then the doubt sets in and she takes a deep breath, faces the nearest Rift, and yells her puppy's name as loud as she can... Only to get jumped the the most terrifying feral abomination of a Direwolf with red eyes and pure evil in it's veins, borderline rabid and foaming at the mouth...
Then she scratches her behind the ear and Nymeria domesticates on the spot. She tells her that Finn and Jake are friends and she gets that big derpy look a bunch of dogs get when they're happy.
Camera cuts to Finn and Jake and they're absolutely MORTIFIED that this MONSTER of a hound is what Arya considers "a cute little puppy".
I just think it'd be funny! (Wish I could draw...)
Alright, let's start sharing more fun crossover interactions/fun headcanons:
Stripe is the only one who understands Taz's 'words'.
Reindog knows what's going on plotwise, but Lebron James KNOWS what's going on and is just playing along with the narrative.
Marvin knows the guy who created the Iron Giant and is confused as to why this destructive robot isn't turning this planet into a wasteland.
Edit: Agent Smith is the only other person who knows they're in a video game aside from Lebron James.