What is the story of Yellow Submarine?

King Features Syndicate did a cartoon show about The Beatles, featuring their music but other people doing their speaking voices. The band hated the show. When the producers (Dunning and Brodax) approached them about doing a feature-length cartoon, the Beatles agreed to it because they still owed United Artists a movie; after Help!, they didn't want to appear in another one themselves. (Magical Mystery Tour was a TV special, not made for UA... and it bombed.) The Beatles contributed ideas, and some leftover songs to give the movie new material; their speaking voices were again supplied by actors. When the band saw the rough cut of the movie they liked it, and agreed to appear in a live epilogue to the story. In the 1970s, Lennon's opinion of the cartoon show softened, and he admitted to a friend that he got "a blast out of watching those old Beatles Cartoons on TV." His son Sean saw Yellow Submarine at his babysitter's house, recognized his dad, and came home asking about the Beatles. Lennon explained that yes, he'd been one, but he gave that up to be with Sean.