"Head" (1968) is an American rock movie starring the American pop group The Monkees.
Zappa has a small cameo in this film (ca 49:05), leading a talking cow and giving David Jones some advice:
FZ: "That song was pretty white."
David Jones: "Yeah, well, so am I, what can I tell ya?"
FZ: "You've been working on your dancing though."
David Jones: "Oh, yeah, yeah, well, I've been rehearsing it. Glad you noticed that."
FZ: "Yeah. It doesn't leave much time for your music. You should spend more time on it, because the youth of America depends on you to show the way."
David Jones: "Yeah?"