From the second episode of The Beatles Cartoon series which ran from 1965-1969.
Episode Summary: John is kidnapped by a mad scientist's assistant. The mad scientist wants to bring to life a Frankenstein type monster and make it a rock star. All she needs is the brain of a beetle (hence the kidnapping of John, the "brain of the Beatles"). John and the monster's brains are switched, and the singing monster is mobbed by a herd of female fans.