Has anyone actually known any dogs named Fido?

No. But i owned a goat once. We kept him on a small island in my pond. We named him gilligan

years ago I met a friend of a friend who invited a bunch of guys to his house to play poker.....but he warned us that he had a "dog" named FIDO and asked to make sure we did not aggravate or try to provoke "Fido" because "Fido" had been known to bite.

So I get there, expecting some KUJO-PITBULL mix only to have this scrawny Siamese cat walk out into the den and the guy say, " This is my dog, FIDO"

My wife is a vet tech so I figured I would get an expert opinion. Her answer... "I don't know"

She did however use the opportunity to ramble off a list of other boring dog names. Sorry OT

One

Known of. No.

I think it would be pretty hilarious if someone had a dog named Fido

Not that I can recall. Although, I had an uncle name his dog, Dog.