Revealing mistake: After Bongo the Gorilla Bouncer tosses Eddie into a pile of garbage cans in the back alley, Eddie lifts himself up and here we can see that he's wearing knee pads beneath his pants. (00:21:25)
Revealing mistake: After Roger reads Marvin Acme's will out loud, all of the toons start jumping for joy. Meanwhile the music machine is still activated in the background, and its colorful flashing lights are being reflected on the ground near Betty Boop and Tweety at the front of the crowd. With all of the toons grouped together like they are, the machine's colorful lights should have been obscured, not reflected. (01:35:30)
Revealing mistake: During the Toon Patrol chase, before the cab enters the alleyway there's a wide shot of the cab making a fast turn. Valiant has his head down, with his hat covering his face and his body totally motionless, opposite to what he looks like in the close-ups where he is grabbing the steering wheel, his head up and controlling the car, thus revealing that the actor was replaced by a dummy in some of the shots. (00:58:40)
Revealing mistake: When Eddy is fighting Judge Doom, Eddy is holding a giant cartoon magnet. He then attracts Judge Doom's sword and when Eddy drops the magnet it is attracted to a steel drum. If you look at the bottom of the drum you can see two strings on the bottom of the drum as it moves towards Bob Hoskins. (01:27:10)
Revealing mistake: When Eddie sits on the bench and the hippo sits down, you can see Eddie bounce off the bench before the bench even moves. (00:09:10)
Revealing mistake: When Roger takes a shot of bourbon and blows his top, it causes most of the glass objects in R.K. Maroon's office to bust into pieces. In some instances you can see an explosive charge breaking the glass - like the giant angel statue at the center of R.K.'s trophy collection. (00:24:00)
Revealing mistake: Just before a conveyor belt drops the vase upon Eddie's head, an overhead shot shows him pointing at Smart Guy, but actually Eddie points much further left in relation to where Smart Guy is standing. (01:25:10)
Revealing mistake: After shooting their way into Eddie's apartment, the weasels start walking in and cast long shadows on the floor. But the only shadow visible in a reflection on the nearby glass doors is that of Wheezy's Tommy gun. (00:41:10)
Revealing mistake: A string is visible suspending Greasy's gun when Smart Guy orders everybody to search Eddie's apartment for Roger. (00:41:55)
Revealing mistake: The streetcar railway tracks are simply metal strips laid in the road. When Eddie jumps off the back of the streetcar's bumper, you can see that the rails are not in full contact with the road, as there are visible gaps between the rails and the road surface. What's more, the rails do not have the grooves that would be necessary for the cars' wheel flanges. (00:10:10)
Revealing mistake: When Eddie is using the magnet to pull Judge Doom toward him, you can see the wires attached to Doom's shoulders used to move him. (01:27:05)
Revealing mistake: Throughout the scene where Eddie is in Toontown, you can find many shots where Eddie is slightly transparent, with the background showing through him. One example of this is when Eddie looks inside the yellow car, and you can see the car through his body. (01:10:57)
Revealing mistake: When Judge Doom gets sprayed by the Dip spraying machine, stunt cables attached to him are visible, pulling him backwards. Christopher Lloyd also seems to have been replaced with a dummy. (01:31:22)
Revealing mistake: When Eddie fires his "Toon" revolver at the whisky bottle, you can see what appears to be a white, plastic model in his hands. This obviously would've been used as a reference for the animation to be tracked onto later.
Revealing mistake: During the climax, one of the weasels says "Toon Town's right on the other side of the wall, boss!" If you look, you can see a brick moving completely by itself behind him. It literally just pushes out of the hole in the wall as though it's being pushed from the other side. It seems like the other weasel was supposed to be animated pulling it out, and they somehow forgot to animate that part. (He does reach over and grab it for a split second... but then immediately lets go for some reason).
Revealing mistake: In the Acme warehouse, Roger's shadow disappears a split second before the bricks land on him. (01:21:50)
Revealing mistake: Eddie heads into Toontown with an oversized animated gun. As he lurks into an alley, his gun is a plastic prop. During filming, Hoskins would carry the prop gun and the animated gun would be superimposed over it, but the animation wasn't applied to the gun in the alley. (01:13:50)
Revealing mistake: After getting a mouthful of soap from Eddie, Smart Guy is thrown across the room and loses his gun. When the gun hits the wall you can see it dangling from a puppeteer's string in mid-air. (00:42:15)
Revealing mistake: When Toon Town's red curtain rises for Eddie in the long tunnel, the reflection on the pavement doesn't move correspondingly. (01:10:00)
Revealing mistake: When a bar of soap knocks Wheezy into the window blinds, he casts no shadow on the wall, but his Tommy gun does. (00:42:30)
Answer: Valiant also shares his name with Arthurian comic strip hero Prince Valiant, who wields a singing sword, Flamberge.