Continuity mistake: When Mr. Feeny is asking the class if they have any comments on Cory's documentary, he calls on Angela, and Cory begins turning his head to look in her direction. When the shot changes, he is instantly looking at her. (00:04:12)
Continuity mistake: In this episode Eric said he was 8 months older than Jack, but in '5-17 And Then There Was Shawn', Jack said that he was older.
Continuity mistake: When Topanga is in the elevator and is saying "We'll just have to let nature take its..." the elevator door completely closes before she can say "course." When the shot changes to Cory saying "Nature take its what?", the door can be seen sliding closed again.
Continuity mistake: When Cory is whispering in Amy's ear, she is holding a cup of frozen yogurt in her left hand. When the shot changes, she is holding it in her right hand. (00:16:40)
Continuity mistake: If you look in most of the scenes, especially the one where she is throwing the stuff out the window, you can see a wall out of the window, but in the scene where Cory comes back from seeing the lady you can see a dresser out the window.
The Witches of Pennbrook - S5-E5
Continuity mistake: When Shawn is saying "So, Rosemary, how's the baby?" his left hand is resting on a box of household items. When the shot changes, his left hand is instantly raised. (00:10:00)
How to Succeed in Business - S5-E9
Continuity mistake: When Amy shows up in Eric and Jack's creative writing class, her backpack is first shown to be unzipped a few inches wide, and just before she sits down, it is suddenly zipped nearly closed. (00:06:20 - 00:07:00)
A Very Topanga Christmas - S5-E11
Continuity mistake: When Topanga tries the egg nog, you can tell that there is nothing in the paper cup.
Raging Cory - S5-E12
Continuity mistake: When Jack is sarcastically asking Shawn if his room is where what people throw down the garbage chute ends up, they are standing shoulder to shoulder. When the shot changes, there is now space between them. (00:02:25)
Raging Cory - S5-E12
Continuity mistake: When Shawn is talking about how the time Cory beat up his dad will be a great memory, the half of a cracker he is eating suddenly has another half-sized bite taken out of it and his hand is near his mouth. When the shot changes, the cracker is half-sized again and his hand is several inches away from his face. (00:03:40)
The Eskimo - S5-E13
Continuity mistake: When Jack is asking Eric about his date the previous night, Eric puts down the book he was reading with the spine facing towards Jack. When the shot changes, the book has now rotated almost 90° counter-clockwise. (00:03:56)
Continuity mistake: When Cory is saying to Lauren "Well, today I guess you're stuck with me," he slightly raises his left hand and then sets it back down on his left knee. When the shot changes, his left hand is suddenly resting on the couch cushion between his legs. (00:05:03)
Torn Between Two Lovers (Feeling Like a Fool) - S5-E16
Continuity mistake: When Eric is saying "You think I should be a teacher," Mr. Feeny has his hands on his hips. When the shot changes, his arms are down by his sides. (00:15:42)
And Then There Was Shawn - S5-E17
Continuity mistake: When Shawn is grilling Kenny about asking to borrow Topanga's pencil, sometimes there is a female student sitting directly behind Angela with an open book on her desk, and other times the desk is unoccupied altogether. (00:00:21 - 00:02:40)
And Then There Was Shawn - S5-E17
Continuity mistake: After Eric rips the receiver and cable off the pay phone, at first he is holding the receiver in his right hand and the cable in the left. A couple of shots later, the receiver and cable have swapped hands. (00:15:15)
And Then There Was Shawn - S5-E17
Continuity mistake: When Feeny appears in the hall, he has his hands in front of him, and he is holding them. When Shawn touches him on the shoulder and Feeny falls on his knees, his hands are still in the same position, but when he is shown lying on the ground, his arms are now be his sides. Feeny was dead, so there is no way that he could've moved his arms.
If You Can't Be With the One You Love... - S5-E18
Continuity mistake: When the transient is asking Cory if he's a cop, he points his right-hand index finger at him. When the shot changes, his index finger is curled onto his thumb. (00:08:20)
If You Can't Be With the One You Love... - S5-E18
Continuity mistake: When Shawn is cracking open his beer, he grips the top of the paper bag between his forearm and upper arm, with the top of the bag level with his shoulder. When the shot changes, the bag is suddenly lower. (00:09:15)
Continuity mistake: After Topanga angrily walks out of Cory's house, he gets out of his chair and says "She really left," with his arms and fingers outstretched. When the shot changes, his fingers on both hands are curled into loose fists. (00:12:40)
Graduation - S5-E24
Continuity mistake: When Jack is showing Shawn the framed caricature drawing, both his hands are holding the frame around the middle of each vertical side. When the shot changes, his left hand is suddenly holding the frame by the bottom corner. (00:06:10)
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.