Chowder - Season 3 Episode 17

Mung tells Chowder that one day he'll have to grow up and run the kitchen on his own once he becomes old enough. Chowder didn't want to grow up and sings a song explaining why, but he sings the same song for twenty years and grows up naturally. He then sees what all of his friends grew up to be, and he finally realizes that he should stop acting like a kid and grow up.