This article is from the Kurt Vonnegut FAQ, by George A Cooley firstname.lastname@example.org with numerous contributions by others.
He appears for approximately five seconds in "Back To School" starring
Rodney Dangerfield. He delivers an essay about himself that Dangerfield
paid him to write. The essay is later graded 'F,' because "whomever
wrote this obviously knew *nothing* about Vonnegut!" (paraphrase)
Bob Weide also reports that Vonnegut does make a cameo appearance in the
new "Mother Night" movie! For more on "Mother Night," again, see
question #18 above.