I must have lived a pretty sheltered life, because I somehow missed this back in 1971. And it has to be one of the weirdest ideas for casting a movie in a long time. It's called "Two Lane Blacktop" and it stars, of all people, the Beach Boys' Dennis Wilson and James Taylor as two drag racers who go on a road trip across America. 

And yes, they fill the roles as actors, not musicians. I'm guessing this isn't as obscure a film as I think it is, but I'd never heard of it until today. And you know what? For two non-actors with little experience in film, they're not half bad. Although it helps there's not a lot of dialogue for either of them.

If you're curious about what these two 70s icons looked like starring in a film at the peak of their youth, you can watch the entire thing free on the Internet Archive here.