A few of his books were made into movies, despite the fact that his prose is more about telling than it is about showing, thereby making his works unlikely candidates for the visual medium. Surprisingly, some, like Slaughterhouse-Five and Mother Night, are terrific. Unfortunately, others, like Breakfast of Champions and Slapstick (Of Another Kind) are completely wretched. There have been others, mostly based on short stories, mostly made-for-television and mostly unavailable. And there have long been talks of adaptations of the novels Cat's Cradle, which Leonardo DiCaprio is trying to make, and Sirens of Titan, which Mother Night screenwriter Robert B. Weide has been interested in for many years.
One of the most random links Vonnegut had to the movies, though, came with the Rodney Dangerfield guilty pleasure Back to School. The writer made one of the most memorable cameos ever, appearing as himself in a sequence in which Dangerfield's character gets an "F" on a paper about Vonnegut. The joke: Vonnegut himself was paid to write the paper. Also, interestingly enough, Back to School co-star Keith Gordon went on to direct Mother Night. Another strange connection came in the late 1990s, when a lot of so-so teen movies were explicitly referencing Vonnegut or his books. I can only remember this definitely being done in Varsity Blues, Disturbing Behavior and Can't Hardly Wait, but I could swear there were more.