Anyone else think that the cats you find wandering about the Commonwealth, are actually synths? It's been stated numerous times throughout the Fallout series that cats are extinct, with most recently Mr. House in New Vegas saying it. Not to mention, we know the Institute is trying to bring back previously extinct species as synths.
Either that, or the Institute got ahold of Mr. Bigglesworth from Dr. Evil while they were in cryo, and cloned the crap out of him. https://www.youtube.com/watch?v=KHYEthYTMhM
https://www.youtube.com/watch?v=jYp7wQk7jts