First off I have to say that I have watched Cracker Jacks video a bunch of times and I'm in love with him!

I could not offer any better advice than has already been given. I'm sure the poor guy is nervous and trying to adjust to his wonderful new home.

I also saw many picker eater kitties get really thin at the shelter. They used only Science Diet and a lot of the cats hated it. They only ate enough to stay alive. I think that an older cat that has been fed something specific most of its life has trouble dealing with new foods. You may just have to find one that he is willing to eat.

Do you know how long he was in the shelter? I wonder if he didn't like their food either and that is what has caused a weight loss. He may have been fed canned food before. You just never know and it takes awhile to get all the kinks worked out. I'd say in about another two weeks you both will have it all down pat!
Getting him a check up won't hurt a thing!

GIANT kissies to CJ and big {{{{HUGS}}}} to you.