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.
Character mistake: After the production assistant walks away from the catering table, he walks into the area where the Matthews are being interviewed. Any production assistant would know better than to just casually walk right into the shot when a live televised interview is going on.
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.
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.