Slap-Stick(s).

Moviefone obtains a full scene from Hitchhiker's (and one not in the book), namely Arthur, Ford, Zaphod, and Marvin trying to cross a field of those slap-happy doodads from the first trailer. A bit goofy on its own, but if the rest of the movie has succeeded into lulling you into Douglas Adams' trademark sense of humor by this point, I could see this being pretty funny.