Truth and Consequences - S3-E7
Continuity mistake: When they catch Janitor Bud on tape, there is a time clock on the wall. Through the rest of the episode there isn't.
Continuity mistake: In this episode, Turner goes into a room and says it's his bedroom. But in "My Best Friend's Girl" Cory goes into that room and they say it's a closet.
Continuity mistake: Shawn steals some fruit just before the interview starts. He empties the whole bowl into his backpack. When the interview starts, the bowl is full again, with the exact same fruits that were just taken by Shawn.
The Grass is Always Greener - S3-E12
Continuity mistake: Early in the episode when Cory is talking to Shawn by their lockers, Shawn closes his locker and you can see one of the straps from his backpack sticking out on the bottom-right side of the locker. A few shots later, the strap is now sticking out on the bottom-left side. About a minute later in the scene, just before Topanga comes to talk to Cory, you can see the strap is now sticking out of the bottom-middle area.
Continuity mistake: When Cory is asking Mr. Feeny to call his parents to pick up him and Shawn, Feeny can be seen removing the white drape from the sofa. When the shot changes, Feeny has instantly removed the drape from the chair across from the sofa as well.
Continuity mistake: When Cory and Shawn mistakenly believe Mr. Feeny opening the door to his cabin to be an axe-murderer, Cory throws his gloves at a nearby chair to grab something to defend himself with. One glove hits the floor in front of the chair, while the other lands on the chair and slowly falls off. A couple of shots later, the glove is back on the chair, while later shots show the other glove to be on the floor by the chair's right armrest.
Continuity mistake: During the first sequence of Eric and Frankie's game of pool, after Frankie's shot, the cue ball is shown slowing to a stop near the center pocket of the table opposite from where Eric is standing. A few shots later when Eric is taking his shot, the cue ball is suddenly near him.
Continuity mistake: When Shawn is loading up his backpack with food from the catering table, a production assistant emerges from the kitchen and asks him if he's part of the interview. After Shawn says he is, the assistant walks away towards the front door. When the shot changes to the couch where the family is being interviewed, the assistant is nowhere to be seen, even though he walked right into the area of the shot. When the shot changes yet again, the assistant is back by the catering table, standing with his arms folded.
Continuity mistake: In this episode Cory has a full length locker, but in the previous episode (Hometown Hero) He has the top locker. It's always in the same stop, so there is no way that he changed lockers.
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.
Answer: Topanga's middle name is never specified. Considering her sister's name is Nebula Stop-the-war Lawrence, Topanga's is probably something equally unusual.