Revealing mistake: In the episode where Teri Hatcher's character is in the supermarket, as you see her place her two items, a carton of OJ and a carton of eggs, listen closely. The items are empty -- quite obviously so. (00:17:45)
Sunday in the Park with George - S1-E21
Revealing mistake: When Morty gets down on his knee to propose to Sophie, the angle of the camera shows the top of the set, which makes it seem as if there is no ceiling to the room.
Answer: He was investigating the lead not the case.