No Such Thing as a Sure Thing - S7-E4
Revealing mistake: The pitchfork that the Amish girl throws at Eric at the end of the episode is obviously made of rubber, as it wobbles when he catches it.
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)
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.