Homer Badman - S6-E9
Character mistake: When Grandpa is putting up the American flag for Homer's public access show and Marge says the flag only has 49 stars, there are actually only 38: 8+7+8+7+8.
Catch A Falling Star - May 21, 1979 - S2-E10
Character mistake: In the preview for this episode, Charlie has trouble getting his countdown straight. He shouts that Sam is on in 50 seconds, then 47, then 48. In the episode itself, the mistake is corrected with a rather obvious overdub, changing the final number to 43. (00:02:05)
Character mistake: Brandon begins the scene giving his speech while he is sitting/leaning on the desk. The students all move into the picture from both sides and gather around Brandon then they all say, "There's No Hope With Dope". After the conversation with Mr. Belding, they watch the commercial they just shot (beginning with each student giving his/her opinion about drugs). Then Zach says his speech while sitting/leaning on the desk. He stands up, the rest of the students and Brandon move in and gather around Zach, then Brandon gives his anti-drug speech.
Hercule Poirot's Christmas - S6-E1
Character mistake: After Japp's arrival, when Poirot walks up the stairs with the two male detectives, at one point he says "Mais no madame." ("But no mylady.")
Character mistake: When Estelle gives her guest speech about the Tuskegee airmen she shows a slideshow. There is a photo of an airplane that she incorrectly labels as "a single engine P-47." This is not correct. The plane in the photo is a P-39 Airacobra. (00:19:45)
Character mistake: The title card says "Plummers Academy" instead of "Plumbers Academy."