You're the Greatest, Charlie Brown (1979)

Signing up late for the Junior Olympics, Charlie Brown becomes a contender in the only available, and most demanding, event, the decathlon. With great difficulty, Charlie Brown, and later Marcie, train for the event. On the days of competition, the pair face the arrogant Freddy Fabulous and Snoopy as well as the "Masked Marvel." During the contest, Charlie Brown proves to be a surprisingly viable competitor.