Crispin Glover almost kicks Letterman in the head
Crispin Glover is best known for playing George McFly in Back to the Future. After the film's success, Glover appeared on Letterman's show in 1987 to promote his next flick, River's Edge. Wearing a wig, glasses, and platform shoes, Glover refused to answer any of the questions Letterman asked him, with the talk show host growing visibly annoyed as time went on.
The show culminated in a dangerous stunt; Glover, claiming to be strong, kicked in the direction of Letterman's face, inches away from delivering quite a bruise. Glover was asked to leave during the commercial break.