Muscle Shirts

Jake wore his one and only undershirt (under his winter-appropriate, long-sleeved shirt) the other day. I didn't think anything of it, until I went to pick him up. He had taken off his shirt, and was wearing only the undershirt with his pants. What a stud (?). Somehow he has taken to "muscle shirts" as he calls them, and has tried to sneak out a few more times with a muscle shirt on under his long sleeved shirt. I think I might have my own set of challenges with Mr. Muscles...