Back when he hosted Late Night, Letterman was the king of weird. For one night in 1987, Crispin Glover outdid him. Without telling anyone — including Letterman — he came in as the bizarre character from his movie Rubin and Ed, acting paranoid and out of his mind, leading to an arm-wrestling match. It was rumored that he was tripping on LSD, which continued since the movie didn't come out until 1991.