Other mistake: In the scene where Yakko, Wakko and Dot are sitting at their desks repeating Miss Flamiel's every word, Wakko is drawn without legs (only feet) during one shot.
Other mistake: While Sonic and Tails are locked up in old Spelunk's cage during the cave-in, right before the huge diamondius crashes on top of the cage, there's a close-up of Sonic holding the bars, and the color of his torso becomes the same as the background mid-shot.
Carnival Knowledge / Sand In Your Navel - S1-E9
Other mistake: [The episode will soon change to "Show Generally"] In the show's introduction, the giant clock comes and smashes a baseball cap on Rocko, growing him up. Then, when the giant blue hand picks him up, the baseball cap disappears mid-shot, with no explanation. (00:00:15)
Beavis and Butt-head vs. the Vending Machine - S4-E28
Other mistake: When Butt-head is purchasing the pork rinds from the vending machine, he notes that the selection for them is F2. When he is pressing the buttons to dispense them, he presses the F button twice, but never the 2 button. Somehow, the machine still dispenses the correct item.