Verne is being pressured by the bully Jackson to swing over Deadman's swamp on a rope to become a member of the Mega-Muscle-Man Club. Verne is skeptical and considered a chicken.
Verne finds his father with Marty; Marty is wearing booster boots-- one of Doc's new inventions. Verne tells them of his predicament. Jules enters with an old box of newspapers. Marty and the boys discover that Doc was involved in Small Town Wrestling in the 1950s. Doc tells them that he was set for a match but never entered the ring.
Verne thinks that if his dad had become a wrestler, the other kids would really think that he was cool. Marty and the boys head back in time to make sure that Doc competes in the match. Once there, Emmett "Brain Buster" Brown enters the ring but gets conked on the head with the hanging microphone. A loopy Doc then believes that he is a superhero-- Mega-Brain-Man!
Wearing Marty's booster boots and the wrestling outfit, Doc scours the city, putting evildoers in their place. As it turns out, "Mega-Brain-Man" constantly mistakes ordinary events as "dastardly" deeds and acts inappropriately. After one incident, Doc regains his memory and is taken back to the ring to finish his match...where he is defeated. He decides to continue his pursuit in science.
Marty and the boys head back to the future. Verne is once again pressured to swing over the swamp and declines, saying that he will follow his instincts. Jackson grabs the rope and swings. The rope breaks and Jackson goes down into the goop... and Verne declares as he leaves, "This is Mega-Brain-Man saying yoicks and away!"