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: 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 Cory is saying to Shawn "Are you going to nice yourself out of the girl you love?", Shawn's right foot is resting on his left knee, and his left hand is on the foot. When the shot changes, his left foot is now resting on his right knee, and his left hand is resting on his left thigh. (00:05:06)
Continuity mistake: When Cory enters the noir world and uncovers Topanga's corpse, you can see her left hand is draped over her stomach. After the noir version of Cory confesses to the murder, the cloth covering her body is now suddenly covering more of her torso, including the left hand. (00:17:53 - 00:19:15)
Continuity mistake: When the noir version of Shawn is asking Topanga what she's running from, the pot of coffee is next to his left arm near the edge of his side of the bar, and the coffee mug is slightly to the left of the crease in the bartop. When the shot changes after she asks him what he means, the mug is now directly over the crease, and the pot is in the center of the bar between the two of them. (00:06:53)
Revealing mistake: When the noir version of Eric is talking about the noir version of Jack as he is playing the piano, you can see Jack is just tapping his fingers against the piano keys and not actually striking them. (00:05:33)
Continuity mistake: When Topanga gets sucked into the time continuum vortex, you can see a teddy bear between the skis and a pair of shoes. When the shot changes to Cory, you can see the skis and the pair of shoes, but the teddy bear is now missing. (00:04:03 - 00:04:33)
Continuity mistake: When Cory is telling Topanga that he wants to be sure Wile E. Coyote will be all right, you can see a single piece of popcorn on the right side of the microwave stand in the background. When the camera switches back to Cory after Topanga assures him he's always all right, the piece of popcorn is now gone. The amount of popcorn on Cory's shirt also decreases in both aforementioned shots. (00:02:15)
Continuity mistake: When Eric purchases Rachel's tank top, the placement of his right hand while holding it changes when he says "I'm a collector." (00:10:43)
How Cory and Topanga Got Their Groove Back - S7-E18
Continuity mistake: When Eric sneezes on Jack's cereal, Jack is holding the carton of milk level with his abdomen. When the shot changes, he has already set the carton down on the counter. (00:04:30)
How Cory and Topanga Got Their Groove Back - S7-E18
Continuity mistake: When Eric is saying to Jack "It was you all along," he points his left-hand index finger at Jack, who is shown writing down the lottery numbers Eric provided him. When the shot changes, Eric is now pointing with his right hand, and Jack's hands are suddenly on his hips. (00:16:40)
She's Having My Baby Back Ribs - S7-E17
Continuity mistake: When Alan remarks that Amy never got her figure back after she gave birth to Eric, her arms are folded. When the shot changes, her arms are down at her sides. (00:10:10)
She's Having My Baby Back Ribs - S7-E17
Continuity mistake: After Cory says "You don't have to tell me that" after Shawn compliments his waffles, Shawn is shown holding the fork pointed down towards the waffles. When the shot changes, he is suddenly holding holding the fork perpendicular to his body. (00:04:35)
She's Having My Baby Back Ribs - S7-E17
Continuity mistake: When Jack, Rachel and Angela start heading to their class, a shot of Topanga shows her holding a slice of pizza slightly raised from her plate. When the shot changes, she is suddenly holding the pizza several inches above the plate. (00:01:04)
Seven the Hard Way (2) - S7-E16
Continuity mistake: When Topanga joins the group hug, the piece of paper that Eric wrote on is underneath her. When Cory joins in, the paper has disappeared. It then reappears when Mr. Feeny dismisses everyone. (00:20:10 - 00:20:45)
The War (1) - S7-E15
Continuity mistake: After Rachel sprays water all over Cory, the amount of wetness on his shirt varies throughout the scene. (00:05:53 - 00:09:05)
I'm Gonna Be Like You, Dad - S7-E14
Continuity mistake: When Topanga, Shawn and Angela are hanging out in Cory and Topanga's dorm anticipating Cory's return from the doctor, the slice of pizza that Angela is eating goes from having a small bite taken out of it, to being halfway gone, and back to having one bite taken out of it. (00:12:07 - 00:14:02)
Other mistake: At the beginning of the episode, Eric talks about how Alan's Navy background will cause him to use any means necessary including torture to find out about his birthday party. Cory chimes in and states that Alan was a cook in the Coast Guard. The plot of the Season 1 episode Kid Gloves concerned a necklace Alan gave Cory for his birthday, which Alan himself earned for placing second in his weight class for boxing in the entire Navy. So either Cory doesn't correctly remember his own father's military background, or the show needlessly retconned it. (00:00:43)
Continuity mistake: When the voice on the intercom is saying "Paging Dr. Chocolate Pudding," Cory's right hand is on Topanga's right arm, and her hands are in her lap. When the shot changes, both of his hands are suddenly resting on his stomach, and her right hand is suddenly resting on his left leg. (00:07:23)
Continuity mistake: When Shawn stands up on the chair to propose a toast, Eric is at his 9 o'clock. When shot changes, Shawn has instantly rotated his body so that Eric is now at his 6 o'clock. (00:16:47)
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.