Having never had either of my cats give up eating I can't fully relate to your problem. (Actually they did when we got our puppy last year, but they eventually got over it). I think, though, if that did happen my first thought would be that they are sick, especially since Rudie did at one time like at least one type of cat food. I think maybe a vet trip to rule out illness might be a good place to start. Doesn't he eat anything at all? Poor Rudie!