Continuity mistake: When Topanga walks away upset from Cory, she closes her locker in such away that the bottom half of it is not flush with the frame. Moments later when Cory and Shawn are talking, the locker is fully closed.
Continuity mistake: When Mr. Feeny hands Cory the CD, Cory holds it between both hands. When the shot changes, he is holding it with only his right hand, while his left arm appears to be folded around his abdomen.
Other mistake: When Cory throws the CD out of his bedroom window, if you listen closely, you can hear the CD land in a soft terrain. However, the next day at school, Mr. Feeny pulls the CD out of his suit pocket and says that it sailed through his living room window and landed on his walnut credenza. If the CD managed to make all the way into Feeny's house, then the sound of it landing would not be audible.
Continuity mistake: When Cory and Topanga are kissing and he puts his hand in her shirt, she stops him and says "what did you think was going to happen tonight?" Then she puts her hand on her lap. In the next shot, her hand is back on his shoulder.
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.