Topaz has had some trouble

Topaz has had some trouble since he has been here, and we haven't been able to quite figure it out.  He threw up his first night, and I thought it was probably just stress from the change.  But then he threw up a couple of nights later, and three times the night after that.  We decided that was due to change in food.  But after returning to his regular food, he threw up again.  The episodes had always occured in the crate -- so we decided it was due to stress from being crated at night and we tried leaving him out.  Unfortunately he still threw up.  It doesn't happen every night.  But it still happens.  I've taken him in to the Humane Society once for a check up and he has actually gained weight.  He continues to eat, drink, play and use the litter box normally, we still have these vomiting episodes.  I will be taking him in again, and hopefully we can figure out a cause.

I've posted a picture of Indigo playing his favorite game of 'attack the carrier'.  The cat carrier sits a top the crate, which means it shakes and rattles when Indigo jumps up on top of it.  Indigo is convinced this is done just to play with him.  He  rolls on the carrier to make it rattle, and then jumps up and pounces on it in response.  Perhaps he thinks something is inside of it.