Catalina Caper (1967)

A beach movie. A scroll is stolen from an art gallery and taken to Catalina Island, where the thieves plan to use it to swindle Lakopolous, a Greek art collector. They plan to show him the real scroll, then deliver a fake. Lakopolous, however, turns out not to be rock-stupid, and tries to steal the scroll himself. Meanwhile, the thieves' son figures out what his folks are up to and cooks up an improbable scheme that will allow him to steal the scroll back and return it. During this, the whole troupe are under surveillance from a mysterious guy who keeps pulling prat falls. All of which is *completely incidental* to the story of the love interest between Don and Katrina, the blonde guy who always has women flocking to him for no perceptible reason, and the "spontaneous" music and dance numbers.