S3E9: Saturdays of Thunder

In "The Simpsons" Season 3, Episode 9, titled "Saturdays of Thunder," Homer discovers that he isn't the father he thought he was after taking a parenting test. To improve his relationship with Bart, Homer decides to help him build a soapbox derby racer for an upcoming race. Bart's initial attempt, a car called the "Lil' Lightning," is a disaster, and he ends up using Martin Prince's high-tech racer after Martin gets injured. On the day of the race, Bart is determined to win but faces tough competition from Nelson Muntz. Despite the odds and the rivalry with Nelson, Bart manages to cross the finish line first, thanks to Homer's encouragement and support. The episode wraps up with Homer and Bart sharing a heartfelt moment, strengthening their father-son bond.