Continuity mistake: Gene Wilder's pencil disappears in the classroom scene. (00:33:30)
Factual error: At the end of the movie, they break out of prison and their lawyer finds them at the hangar. She tells them they are free and they celebrate and get in the car and drive off. Innocent or not, they broke out of prison. I highly doubt red tape would allow an official to say, "Oh well, never mind, we were gonna release them anyway." (01:46:25)
Continuity mistake: When Harry says the word to trigger the bull, the bull runs out at him and has horns. But in another shot later, the "bull" seems to have become a cow (with no horns).
Visible crew/equipment: At the end, when Gene Wilder stops the car in the desert and jumps out, several large studio lighting panels are reflected in the car door. (01:45:00)
Plot hole: The six-year-old girl (who actually looks a few years older) apparently had seen and remembered a tattoo on the robber's hand well enough to be able to relate the details of it to Meredith, who is then able to visually identify the tattoo on the robber's hand in a strip joint. Not really credible - especially as the woodpecker costumes covered up pretty well the entire body! (Also, the robbers were constantly moving, making visual inspection even more difficult).
Continuity mistake: The first time Skip meets Meredith, and Meredith announces her intention to get a job at the strip club, this part has obviously been added later as an explanatory afterthought and is not well integrated: the lighting, audio and Williams' demeanour do not match the rest of the scene.
Other mistake: When Skip emerges from the box where he has been locked up for five days, he has no more than about one day's stubble on his unshaven face.
Chosen answer: Because his employers discovered he had put grass (marijuana) in the salad and got all the dinner guests high. Well, he didn't, the cook did. But he brought it into the house so he was fired.