A Long Walk To Pittsburgh (1) - S4-E16
Character mistake: After learning that Topanga will be moving to Pittsburgh, Cory tries to rationalize their desire to be together for the rest of their lives despite still being so young by comparing their relationship to that of Romeo and Juliet, thinking they turned out OK. Shortly thereafter, he is shown reading the book in his backyard and explains the situation to Mr. Feeny, who advises him to skip to the end to find out what happens to their relationship, much to Cory's dismay. The problem is that Cory already learned the fate of Romeo and Juliet in Mr. Feeny's class in the first episode of the series. He was even dismissive over the idea of a man killing himself over a woman.
Continuity mistake: When Alan is saying "It's a miracle bra, honey, get a camera," his left hand is resting on the table. When the shot changes, his left hand is suddenly resting on his right arm. (00:08:00)
Continuity mistake: Establishing shots of the Matthews' house show the doorknob on the exterior of their front door to be on the left-hand side, but shots from inside the house show it to be on the right-hand side.
Continuity mistake: When Eric is suggesting to Mr. Feeny that they go out and look for women, some shots show Feeny gripping his wine glass, while other shots show his hands down on the table with the glass several inches away.
Continuity mistake: When Mr. Timmer picks up the mini vase, just before Cory tells him to put it down, you can see he is the only one touching it. When the shot changes, Mr. Timmer and his wife are both holding onto it. Cory also instantly has his left arm raised and index finger pointed at the Timmers.
Continuity mistake: When the bartender fills up the mug of root beer, after the foam settles, the mug is a little more than half full. When Mr. Feeny hands the mug to Eric, it is suddenly filled closer to the top.
Continuity mistake: When the bartender fills up the mug with root beer, the foam has instantly settled when the shot changes.
Continuity mistake: When Eric is performing his one-man show, he states in the intro that he was born on June 24, 1978. However, in the season 1 episode "It's a Wonderful Night," Eric fails his test to get his driver's license. That episode takes place during the middle of the school year, but if Eric was born in late June, he would have had to wait until after, or at the least the very end of the school year to try and get his license, as the minimum age in Pennsylvania for obtaining a driver's license is sixteen.
Sixteen Candles and Four-Hundred-Pound Men - S4-E9
Factual error: The match between Vader and Jake the Snake is supposed to be taking place in Philadelphia, presumably the Spectrum, but the establishing shot of the building is actually the Great Western Forum in Inglewood, California.
Continuity mistake: When Topanga walks away upset from Cory, she closes her locker in such away that the bottom half of it is not flush with the frame. Moments later when Cory and Shawn are talking, the locker is fully closed.
Continuity mistake: When Mr. Feeny hands Cory the CD, Cory holds it between both hands. When the shot changes, he is holding it with only his right hand, while his left arm appears to be folded around his abdomen.
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.
Janitor Dad - S4-E6
Deliberate mistake: Chet comes home from his first day as school janitor brandishing a paycheck, which impresses his wife and in turn changes Shawn's mind about Chet working at the school. Being that it was Chet's first day on the job, there's no way he would already have received a paycheck. Even if it was payday, his employment would have begun on the first day of the next pay period.
Suggested correction: It's possible it was pay for training or orientation days that were before his official start date.
Continuity mistake: When Virna is standing in the doorway of the trailer, her left arm is touching the curtains near the door. When the shot changes, her arm is instantly down at her side.
Factual error: In this episode, Eric and Cory stop in Pottstown, Pennsylvania on their way back to Philadelphia. Cory protests, reasoning that stopping there is pointless because they are only three hours from home. Pottstown is roughly 40 miles from Philadelphia. It certainly wouldn't take three hours to get to one location from the other under normal driving conditions.
Hair Today, Goon Tomorrow - S4-E2
Continuity mistake: When Dylan is asking Topanga out, his locks of hair alternate between being by his face and behind his ear.
Revealing mistake: When Topanga emerges from the kitchen with more ice for Cory, instead of seeing the kitchen through the open doorway, you can see a wall with framed pictures, suggesting another set was there in place of the kitchen.
Truth and Consequences - S3-E7
Plot hole: In this episode, it is discovered through a scientific study that Eric does not dream, and in fact doesn't even register brain activity while he is sleeping. However, the season 2 episode "Wrong Side of the Tracks" features a subplot where Eric listens to a motivational tape while he sleeps so he can learn to ice skate, and he dreams of Nancy Kerrigan giving him a lesson.
The Heart is a Lonely Hunter - S3-E15
Other mistake: Dana exits Chubbie's and sees Shawn has set up a picnic for her. She remarks that it's the middle of winter and Shawn is shaking from the cold, but her breath is not visible.