There's virtually no plot that gets us the singing. Almost everything in creation starts heading somewhere: animals, vegetables, inanimate objects. All are trying to get to a park to celebrate the summer. There is one group of cats that do a sort of Maypole thing with a giraffe. A rather depressing thing is a group of mice being eaten by a hungry hippo. The song is part of our past culture. It's a happy song and is the next in this long line of sing-alongs.