We found his former owners. They had no intention of having him fixed or getting him his shots. He's 5 months old, they decided he wasn't as cute, so they just let him out to roam. They told us to keep him, they were going to move soon anyway and were just going to leave him. (I hate people!)
So, anyway, he went to the vet and was tested for feline hiv and leukemia, both were negative so he got all his shots, got flea treatment and dewormed made himself at home on our couch and has been re-christened Rex (Kittysaurus Rex, thanks to my dino obsessed 9 year old). He will be neutered next week. My 15 year old grumpy old man cat is less than pleased, but he'll get over it.