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.
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.