I always thought they could run though the Rocky movies. A midcard guy that never really went anywhere gets a shot at a cocky champ who has beaten everyone, manages to go to a time limit draw.
Champ demands rematch to prove it was a fluke. Underdog wins title. Underdog gets a string of victories over less than optimal opponents while a heel comes up through the ranks destroying everyone and calls him out. Heel beats him for the title, and Underdog has to prove to himself he's a champion by winning it back. And that's just the first 3 movies.