Simpsons Season 6, Episode 1: Bart of Darkness

A heat wave is gripping Springfield and the townspeople attempt to cool down. Bart and Lisa persuade Homer to buy them a swimming pool, which proves popular with the town's other children. Bart ends up breaking his leg when he dives off his treehouse and is forced to spend the rest of the summer in his room. Realizing that he has become isolated, Lisa gives Bart her telescope to cheer him up.