Some random gag character in the Marvel Universe that is somehow prettypopular and incredibly powerful.
The fact that Marvel even made a character like Squirrel Girl shows how they either aren't aware that Rule 34 exists or don't care enough to think twice.
What da young NASA engineer Mark Rober discovered dat "Phat Gus" was during his "ninja-warrior obstacle course" squirrel-feeder experiment.
After discovering dat "Phat Gus" was "not a dude" (said gray chatterer was so roly-poly --- and had such a prodigious appetite --- due to being FULL OF BABIES, not from overeating), Mark Rober renamed his smallfurry "girl-squirrel" friend "Phantastic Gus".