The Mouse That Roared (1959)

A small country, maybe populated entirely by Peter Sellers, decides to invade the United States and—because their tiny Peter Sellers army arrives during an air-raid drill—the invasion succeeds. Then there's a car chase on a country road. (During the air-raid drill, teenagers might be dancing to rock'n'roll music.) This movie is satirical somehow, as are all films in which Peter Sellers plays multiple roles. Here's another movie I can't see being much longer than 20 minutes.

Ooh, Jean Seberg!