Other mistake: When Cory goes into the apartment and starts to film Shawn and Jack fighting, he is sitting on the coffee table behind them. When what Cory is filming is shown, the camera is facing their sides, not their back. (00:10:47 - 00:11:11)
Other mistake: As Wendy is leaving the apartment, she writes her phone number on Shawn's palm and tells him to call her. She only scribbled a few lines on his palm for a second, not nearly enough time to write her entire phone number down.
A Very Topanga Christmas - S5-E11
Other mistake: When Topanga knocks on Cory's door at 3:00 AM, he comes out and expresses that he's always asleep at this time of night. Despite this, he shows no signs of having just been awakened from his sleep. On the contrary, he appears very alert.
The Eskimo - S5-E13
Other mistake: When Shawn is saying "Thanks a lot Topanga" after she falls to the floor, he is looking down directly in front of him, but she is to his left.
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.