I admit, it's been a while since I really looked into comic book characters. So, I guess I've been taken by surprise about this comic book character, Squirrel Girl and her populatrity.
She's a mutant in the Marvel Universe, with...yes, the proportional strength, agility, biting and claw powers of a human sized squirrel. Plus, she has defeated some rather potent Marvel villains.
The picture links to the Wikipedia article about her.