Continuity mistake: When Topanga is telling Cory that she had her internship interviews in the morning, her arms are folded. When the shot changes, her arms are down at her sides. (00:07:39)
Continuity mistake: When Eric is hugging Angela, her arm is on his shoulder. In the next shot, when Jack is saying "How am I going to survive without money?" you can see, between him and Rachel, that Angela now has her arm on Eric's back. (00:16:58)
Continuity mistake: After Topanga and Angela hug, Angela puts her hands on Topanga's arms. When the shot changes, Angela's arms are suddenly down at her sides. (00:18:27)
Continuity mistake: After Eric pulls the doll from out of the grill, he closes the lid. The lid then alternates between being open and closed throughout the rest of the scene. (00:03:44 - 00:06:15)
Other mistake: Eric is showing Feeny the doll he has and pulls the string to make it talk. When he makes the doll do mission impossible, he pulls the string but the doll doesn't say anything. (00:03:47)
Continuity mistake: In the season 7 episode "I'm Gonna Be Like You, Dad" Alan and Amy's youngest son Joshua is shown to be an infant. However in this episode, which takes place roughly 4 months after the aforementioned episode, he is shown to be around 2 years old.
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.