You're the Greatest, Charlie Brown (1979)
Signing up late for the School Olympics, Charlie Brown becomes a contender in the only available, and most demanding, Olympic event, the decathlon. With great difficulty, Charlie Brown, and later Marcie, train for the event. On the day of competition, the pair face an arrogant opponent and Snoopy as well as the "Masked Marvel." During the contest, Charlie Brown proves to be a surprisingly viable competitor.