Rocco never liked clothes at all, until I found a certain cut/fit of thin sweater that he will wear when it's really cold in the winter. He will only wear a certain material, no sleeves,hoods, etc, and it has to fit a certain way otherwise he has nothing to do with it.
Funny thing is not only does it keep him warm, he completely turns into a couch potato when I put it on. I think it functions similar to a thunder shirt and gives him some security.