Please remember that Cracker Jack has been through a lot lately. With Peanut hissing at him, his new home, and the "fresh" scent of Tubby still around, plus we don't know how long he has been in the shelter, how long its been since he lost his owner, etc. You too would be under a lot of stress if all this happened to you!

I agree that he needs to be check by the Vet for the obvious things, but this all may be stress related. Cats do NOT like change in their life, and poor CJ, he has had a lot of change lately!