"Tell a Joke" is a Sesame Street song sung by Harvey Kneeslapper. In the song, Luis is feeling glum, Susan is feeling a bit tired, and Bob is feeling terrific. However, Bob informs them that they'll all feel worse in a moment, because he sees Harvey Kneeslapper coming by. Harvey wants to tell them a great joke, but they aren't in the mood for jokes, which Harvey says is the best time for jokes, as he sings a song about telling jokes. During the song, he tells a number of jokes, which make the others leave one by one before the song is finished.