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.