Continuity mistake: When the bartender fills up the mug with root beer, the foam has instantly settled when the shot changes.
Continuity mistake: When Amy is trying to get Alan to back off Mr. Mack, the way her hand is gripping his arm changes between shots. (00:16:45)
Visible crew/equipment: When Eric jumps out of his chair and exclaims "No" during his college acceptance interview, a boom mic can be seen being pulled out of view. (00:19:00)
Other mistake: When Cory goes into the apartment and starts to film Shawn and Jack fighting, he is sitting on the coffee table behind them. When what Cory is filming is shown, the camera is facing their sides, not their back. (00:10:47 - 00:11:11)
Continuity mistake: In the beginning of the show, Cory is showing Shawn something he wrote in the school paper. Cory walks away leaving his backpack on the bench. In this whole scene to the point where Cory says, "Is it just me or is it just me" sometimes he is wearing his backpack, and sometimes he isn't. (00:00:20 - 00:03:05)
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)
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)
A Long Walk To Pittsburgh (1) - S4-E16
Continuity mistake: After Cory finishes downing his soda, he places the cup on the table. When the shot changes, his hand is instantly away from the cup. (00:16:37)
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)
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
Revealing mistake: When Shawn unmasks the killer and it is revealed to be himself, you can see that the body double that does the unmasking has sideburns and extra scruff on the back of his neck, making him noticeably distinct from Shawn. (00:18:17)
Continuity mistake: At the end of the episode, when Alan is about to eat the cookie and Amy shows him what she is wearing, he drops the cookie onto his stomach. Later when Amy whispers something in his ear, Alan gets up but the cookie is gone.
Continuity mistake: During the first sequence of Eric and Frankie's game of pool, after Frankie's shot, the cue ball is shown slowing to a stop near the center pocket of the table opposite from where Eric is standing. A few shots later when Eric is taking his shot, the cue ball is suddenly near him.
Revealing mistake: During the montage of Eric and Frankie's game of pool, at one point Frankie hits two balls that spin towards a pocket in unison. When both balls come to a stop, you can see a dent in the green ball where a wire or other device would have been inserted to keep the balls linked together.
Continuity mistake: When Cory and Shawn mistakenly believe Mr. Feeny opening the door to his cabin to be an axe-murderer, Cory throws his gloves at a nearby chair to grab something to defend himself with. One glove hits the floor in front of the chair, while the other lands on the chair and slowly falls off. A couple of shots later, the glove is back on the chair, while later shots show the other glove to be on the floor by the chair's right armrest.
Continuity mistake: At the end of the episode, when Cory and Topanga are kissing, Shawn says "Hey, I'm talking to you", hits Topanga on the arm and her hair gets messed up. When the shot changes to a wider view, her hair is not messed up. The position of Topanga's arms wrapped around Cory also changes.
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.
Continuity mistake: When Cory and Topanga are kissing and he puts his hand in her shirt, she stops him and says "what did you think was going to happen tonight?" Then she puts her hand on her lap. In the next shot, her hand is back on his shoulder.
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.
Chosen answer: In the present day, with the United States abiding by more stricter school health laws, for the most part this wouldn't be in school cafeterias as many cannot even have carbonated beverage machines now. However, in the 90s when the show takes place, it wasn't unheard of for there to be coffee machines in the cafeteria of small schools where the teachers eat with the students as we see them do often in the show. The idea being that the cafeteria was small enough so a teacher or hall monitor could catch a student before they could drink the coffee.