Continuity mistake: After the opening credits, when it cuts to the overhead shot of Shannon sitting on the ground, he has a newspaper covering his head with its front page facing up. In the next shot, the newspaper over Shannon's head has a different front page. (00:06:00)
Continuity mistake: When the gang make a second visit to the waste ground to test the go kart's new engine, Patchy is wearing a light coloured skirt, a button through front jumper and shoes. She is also carrying a small bag. In the next shot she is wearing a different skirt with pockets on the front, a different jumper with no buttons on and boots, and the bag she was carrying has also gone. In the last shot of this scene she is back to the clothes she was wearing at the start. (00:19:35 - 00:21:40)
Factual error: At the start of the excommunication scene, the monks are chanting Dies Irae, a thirteenth century Catholic poem, but St. Thomas Becket died in 1170, almost a century before the poem was written.
Continuity mistake: Ingrid Bergman is sitting in the foyer of the hotel she is staying in. She orders a martini, which arrives pronto, but in the first shot, she picks up the drink and has a sip, and in the second shot, she isn't holding the glass anymore.
Visible crew/equipment: The shadow of a camera and cameraman are revealed on the left side while the President (Frederic March) is moving from one room to another (door jamb), after learning about Martin Balsam's death. (01:20:00 - 01:21:00)
Continuity mistake: In the interrogation room, Leo's right hand instantly moves from being at his side to his right cheek.
Continuity mistake: The three enter a small cantina and start a fight and fire. The place is huge on the inside, with stairs to a second floor. From the outside it's just a small shack.
Factual error: In reality, Commodus did not die in the arena - he was strangled in his apartments in 192 A.D. by an athlete who was hired by a group of Senators conspiring against him.
Factual error: In a scene set in 1871, several newspaper articles get printed on Moe's face as he falls onto a printing press. Curly Joe reads that "AT&T is splitting two for one." American Telephone and Telegraph Company was founded in 1885.
Audio problem: When the Big Bad Wolf is blasted through the wall a second time, we cut back to Bugs who says "I don't see why anybody thinks these club initiations are dangerous." When he says it, the audio is a few frames behind his mouth.