Factual error: When Doom reaches into the cab of the Dip vehicle and starts it, it doesn't jump. It is a modified military vehicle, and it's a standard. If you try to start a standard vehicle without pressing the clutch in to disengage the gears (the weasel driver left it in gear when he died), then the vehicle would lurch forward as the engine turned over.
Revealing mistake: In some shots with the red cars, such as when Benny, Eddie, and Roger are about to crash into one, look at the wheels. The trucks appear raised with a third, large wheel in the center, obviously a road vehicle outfitted to look like a streetcar.
Factual error: The red cars are seen traveling with poles raised on both ends. The wheel at the raised end of the pole, which collects power from the wire, must always be trailing the car. Basically, streetcars going forward have the rear pole raised and front pole lowered, and vice versa. They would not be traveling at normal operating speeds with the front pole raised, as that would damage the wiring system.
Continuity mistake: The number of wood slats on Baby Herman's playpen keeps changing at the start of the film. When his mom says goodbye there are eight slats at the front, and five at the side. When he escapes the playpen there are eight at the side, and when Roger realizes the playpen's empty, there are nine at the side and seven at the front. Additionally, the characteristics of the teddy bear changes, as well as the colors of the balls on the wood slats. (00:00:40)
Continuity mistake: When the officers are carrying Marvin Acme's gurney away, one of them bumps into a crate of squeaking shoes. As the crate topples over, its lid flips upside down between cuts. (00:30:25)
Continuity mistake: As Roger and Jessica get tied to the hook, Wheezy and Stupid switch places between shots. (01:22:15)
Revealing mistake: When Eddie's Plymouth skids out from R.K. Maroon's lot, a large section of the Red Car's railway track gets torn from the pavement with the greatest of ease - revealing that the track is actually just a set of metal strips laid out in the center of the road. (01:07:40)
Continuity mistake: At some point during the opening cartoon short, Roger drinks a bottle of Acme chili sauce and flies directly into a wall-mounted ironing board. The ironing board has a handle on its left side - which vanishes between shots. (00:03:10)
Factual error: At the moment R.K. Maroon gets shot and killed in his office, look at the framed poster of Pistol Packin' Possum that's dated MCMXXLVIII. In Roman numerals, two X's never appear before an L - which makes this a bogus date. (01:07:10)
Continuity mistake: In the scene where Valiant is in the bar and just learned that his friend has been laid-off he takes a drink but Dolores puts her hand over it. In the next shot she has a shot glass in her hand and a bottle, but when Valiant shows her the check, both the glass and the bottle are gone. (00:12:00)
Continuity mistake: When Eddie goes to meet Maroon with his accusations, Maroon is holding a distinctively brass colored gun. When Eddie attacks him, the gun is released by Maroon, and it instantly cuts to a shot of Eddie on top of him, an identical gun in hand. Then when they get up, Eddie tosses the gun aside. When Doom shoots Maroon through the window, Eddie dives for cover and once again the gun is amazingly in his hand. (01:06:20 - 01:07:15)
Factual error: Eddie Valiant borrows Deloris' camera to photograph Jessica playing "Patty Cake". There were at least 13 photos from a roll of film that could make only 6 or 8 shots.
Continuity mistake: When Eddie gets the camera from Dolores, the way he holds the camera changes in the next shot. (00:12:15)
Answer: Valiant also shares his name with Arthurian comic strip hero Prince Valiant, who wields a singing sword, Flamberge.