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.
Other mistake: When Eric and the other security guard discover Mr. Feeny entering the school, Feeny expresses that Eric snuck up on him. Eric was five feet away from Feeny when he first saw him, and was also talking loudly when making his approach towards him. There's no way Feeny couldn't have heard him.
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.