Other mistake: When Mr. Feeny is telling the story about Topanga and Cory in the first grade, he mentions that Shawn told him to leave them alone. However, the season 3 episode "City Slackers" established that Shawn wasn't in school with Cory and Topanga until he was around 12, and that he was in and out of 5 schools in different states before then. (00:18:40)
Factual error: The Starry Night painting that characters look at in the Van Gogh exhibit is mentioned as being the original painting itself. However, if you compare the painting presented in this episode with the real-life painting that is displayed in the Museum of Modern Art, you can see that it is an imitation, as the colors are brighter and the little details in the painting are not as prominent.
Revealing mistake: When Topanga is picking up the letter off the ground, you can tell the snow isn't real because it doesn't behave like real snow and run together when she scrapes the letter against it. It looks more like shredded paper being swept aside. (00:20:38)
The Eskimo - S5-E13
Character mistake: In the opening scene, Cory remarks that they have been in high school for 4 years and there's nothing left for them to be taught. They began high school in 7th grade and are now midway through their senior year, so they have actually been in high school for 5 and a half years.
Suggested correction: There's a difference between being at the same school and being in high school. For most students, high school is 4-years long (9th-12th grade). When I was in kindergarten, I went to a K-12 school. If I graduated from that school, I wouldn't have said I was in high school for 13 years.
It's openly stated numerous times beginning with season 2 when they are in 7th grade that they are now in high school. The school is even called John Adams High School, and not something like John Adams K-12 or anything like that. I remember being baffled by this growing up, because high school for me did not begin until 9th grade, and even then, we didn't attend an actual high school until 10th grade. It may be unconventional compared to real life, but the show firmly established that they were in high school starting with 7th grade.
Other mistake: As Wendy is leaving the apartment, she writes her phone number on Shawn's palm and tells him to call her. She only scribbled a few lines on his palm for a second, not nearly enough time to write her entire phone number down.
Other mistake: When Eric and the other security guard discover Mr. Feeny entering the school, Feeny expresses that Eric snuck up on him. Eric was five feet away from Feeny when he first saw him, and was also talking loudly when making his approach towards him. There's no way Feeny couldn't have heard him.
Other mistake: When Eric asks Mr. Williams why everyone is applauding Frankie missing a shot in their game of pool, Mr. Williams notes it's because no-one has ever seen two people play for three hours without sinking a shot. However, if you rewatch a couple of times the part where Frankie takes his shot and you count the balls on the table, there are only 14, not including the cue ball, when there should be fifteen. If by chance a ball was knocked off the table, then given how much the crowd was into the game, someone would have told them they needed to place the ball back on the table.
The Pink Flamingo Kid - S3-E17
Other mistake: When Eddie busts Cory filming him and his cronies, he spends a few moments intimidating Cory before snatching the camera out of his hands and throwing it against the ground. After Shawn breaks up the situation and notes that they broke the camera, Cory remarks that they didn't get the tape and proceeds to pull a tape from under his jacket. Cory's hands are both visible gripping the camera the entire time that Eddie is confronting him, and he didn't have the opportunity to retrieve the tape when Shawn intervened, so he couldn't have had the tape tucked away.
Deliberate mistake: When Alan is trying to rush Amy out of the door, she yells from upstairs that she's still shaving her legs. A mere 20 seconds later, she comes downstairs wearing a dress and nylons. Even if she was for some reason shaving her legs while wearing a cocktail dress, that still wouldn't be enough time for her to clean off her legs, put nylons on and then walk downstairs.
The Last Temptation of Cory - S3-E9
Continuity mistake: When Shawn walks out of the front door of the Matthews' house, you can see some diamond fencing with vines on it on top of a brick foundation. But establishing shots of the house show no such feature by the front door.
Deliberate mistake: Morgan turns on the stereo and starts dancing on the sofa with her doll. She then tosses her doll, which tips over a plant and breaks the glass on a set of French doors. The stereo magically stops the moment the glass breaks.