Plot hole: After Shawn leaves Cory's house to get a pizza, he calls Cory on the phone literally a minute later to tell him that Lenny Dykstra is at the pizza place. There's no way Shawn could have left Cory's house, walked to the pizza place, spotted Dykstra and either asked to use the restaurant's phone or found a pay phone to call Cory in such a short amount of time. (00:13:30 - 00:14:45)
Truth and Consequences - S3-E7
Plot hole: In this episode, it is discovered through a scientific study that Eric does not dream, and in fact doesn't even register brain activity while he is sleeping. However, the season 2 episode "Wrong Side of the Tracks" features a subplot where Eric listens to a motivational tape while he sleeps so he can learn to ice skate, and he dreams of Nancy Kerrigan giving him a lesson.
The Witches of Pennbrook - S5-E5
Plot hole: In this episode Cory takes Topanga on her "first airplane ride". But in season three (episode 66), Topanga had to go Disney World and she obviously took a plane.
Plot hole: At the beginning of the episode, Eric and Jack call the cops on Luther for planning an illegal rave at the college, but the cops let him go because he had not started the rave. He still broke into the student union building, and therefore should have still been arrested. He even threatens Eric and Jack afterwards right in front of the cops, and they do nothing about it. (00:00:20 - 00:02:10)
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.