For people who don't want to watch, Sabat had a key to Sean's room and while he and Sean were at a recording session gave it to some people who snuck into Sean's room to subtly mess with it. They replaced his toothbrush with a different looking one, put a kazoo in a pair of pants he brought with, and a few other innocuous things to make him think he was crazy. Then they did it a second time and did more weird stuff with a kazoo and made him think it was one of the hispanic cleaning staff.
Kind of a funny prank, but I don't know Sean so he may have really not appreciated it. From the end of the story it doesn't sound like Sean was overly upset about it, but then again it's Sabat telling the story.