Up! (1976)

This kicks off with the murder of one Adolf Schwartz (who bears a striking resemblance to another famous Adolf) via the placement of a ravenous piranha fish in his bathtub. Who did it? No-one knows or cares, as they're too busy being distracted by busty Margo Winchester, who hitchhikes into town and gets involved with all the local men. It ends with a series of complicated plot twists that reveal that just about everyone is really someone else. And if it gets too confusing, Russ Meyer helpfully arranges for a one-woman nude Greek chorus to pop up at intervals to explain what's going on.