(Video Link)
For this clip from Late Night with Jimmy Fallon, Paul Reubens voiced over all of the dialogue using the many tones of Pee-wee Herman. But that's just a taste of the entire film, which is excellent, except for Chairry's horrible, horrible death scene.
-via Nerd Approved
http://twitter.com/peeweeherman/status/223818625621045248
Although he doesn't make it clear if that's his voice.
http://www.youtube.com/watch?v=wDK8Y5X8WI4&feature=related