Deliberate mistake: Rather than using real Bruce Lee footage only for the final fight scenes, so the undisguised Billy Lo's different appearance might make sense after his surgery, the filmmakers instead spliced real Bruce Lee face footage throughout the early film giving the character a constantly changing face from scene to scene.
Deliberate mistake: When the father jumps on the firemen's jumping sheet, one can see that he's very few centimetres away from safely landing on it. However, in the immediate close-up he crashes against the floor, which is more dramatic, but ludicrous nonetheless.
Deliberate mistake: Before Superman traps the black missile, its beam is really big and covers half of the lettering on the side. When Superman is behind, the fire is much smaller and the lettering is visible, allowing us to see Superman.