That is just toooo funny!!!
Keep putting it on him though, he will most likely get used to it.
Rowdy was the same way with his sweater when I first put it on him. Now mind you, we were in the mountains and it was freezing and he was shaking when he had to go potty, but when I'd put the sweater on him, it was like he had rigormortis - he was stiff and wouldn't move a muscle. When we came home, I kept trying to get him to wear the sweater but got the same reaction. Then one day when I put it on him, the black lab next door started barking like all get out. Rowdy heard him, raced out the doggie door with the sweater on and ran up and down the fence barking like crazy too. From that day on he has been fine in his sweater. I guess he must have thought he wasn't supposed to or couldn't move!