Trivia: Jeff East, who plays teenage Clark Kent, was dubbed over with Christopher Reeves' voice. The only time Jeff's actual voice is heard is when he shouts in excitement after jumping past the speeding train.
Trivia: Two of Bruce Lee's earlier films, The Way of the Dragon and Fist of Fury, are seen as films Billy Lo (Bruce Lee) is starring in, Fist of Fury being the one where Billy is shot.
Trivia: When everyone's back at Sonny's ranch watching his old stunt films, the footage with him getting thrown from a canoe in a river was from his movie "Deliverance".
Trivia: The role of Philo Beddoe was originally written for Burt Reynolds.
Trivia: The Chetniks were not one coherent group, as portrayed in the movie. There were in fact two opposing fractions: the first fought alongside the partisans, the others - founded by Kosta Pecanac (the featured group) cooperated with the Germans. Despite their public enmity, though, they still maintained good relations with each other, one of the facts which led to great confusion about the Chetniks among the Allies - probably the reason why they are portrayed here solely as 'bad guys'.
Trivia: Irwin Allen was so disheartened by the amount of money he lost on this film that he forbade any of his employees to ever mention it again, and even cut short an interview when a question was asked about it.