I think Iron Man would be really funny as a cat. He's used to his high - tech suit and all his gadgets, but as a cat, he has to rely on his cat - like abilities. He'd probably try to build tiny cat - sized tech, like a cat - jetpack or something. And his cocky personality would still be there, meowing sassily at the other Avengers - cats. His sleek cat form with his red and gold fur would be quite a sight.
Hulk would be the most hilarious. Imagine a huge, green cat with a short temper. He would probably be constantly knocking things over with his big cat paws and getting frustrated when he can't smash things as easily as he could in his normal form. His attempts to roar would come out as a strange meow - growl combination that would be both intimidating and comical at the same time.
Thor would be quite hilarious as a cat. He's a god used to his mighty hammer, but as a cat, he'd be this big, furry, golden - haired cat. He might try to summon lightning while in cat form and end up just getting his fur all ruffled. His noble demeanor would be a bit out of place on a cat, and his attempts to communicate in his usual grand way would be reduced to meows and purrs, which would be really funny.