Simpsons Season 9, Episode 23: King of the Hill

Bart becomes disappointed with his father after he is unable to finish a race. Seeing this, Homer decides to go to a gym every night to exercise, while eating an energy bar called "Powersauce" and being trained by Rainier Wolfcastle. Soon, Homer is much slimmer and more muscular. One night at the gym, two representatives of the energy bar come to Wolfcastle to try persuade him to climb Murderhorn Mountain, the tallest mountain in Springfield, as a publicity stunt for the energy bar.