She's Having My Baby Back Ribs - S7-E17
Continuity mistake: When Cory gets off the bed he leans against the dresser and his hands are behind him. When Topanga walks in the room, his hands are by his sides. (00:03:50)
The War (1) - S7-E15
Continuity mistake: When the show starts, Angela and Shawn are kissing. The shot changes to Topanga and Cory, who has popcorn on his shirt. The shot goes back to Shawn and Angela, when Cory is shown again, the popcorn is gone. Again the shot changes to Shawn and Angela, then back to Cory and the popcorn reappears.
Continuity mistake: When the spider is walking on Eric, it makes it past his fingers and has some legs on his wrist before the shot changes. In the next shot, the spider is still walking on his fingers. (00:16:17)
Revealing mistake: When Eric tells Cory and Shawn that the hot chocolates were $4, Cory looks up at the prices and says "that's the retail price." As the scene and the rest of the episode go on, if you pay close attention to the sign that has all the prices, hot chocolate is not an item.
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.
No Such Thing as a Sure Thing - S7-E4
Revealing mistake: The pitchfork that the Amish girl throws at Eric at the end of the episode is obviously made of rubber, as it wobbles when he catches it.
Other mistake: After Jack and Rachel tell everyone they broke up and Angela says to Shawn "Friends, okay?", the camera is noticeably out of focus and then comes into focus when Shawn says "Hate you or love you..." (00:05:10)
Factual error: When Cory and Topanga first enter their new couples dorm, they discover it to be a dump. The entire dorm is filthy, cabinets are falling apart, there are large bugs crawling on the floor, and there is no clean running water. Student housing laws would require the university to restore the dorm to liveable conditions before any student could move in. If the health department saw the conditions of the room, the university would undoubtedly be fined for failing to take corrective action. (00:07:45 - 00:10:36)
Character mistake: After Cory and Topanga have their argument in front of everyone, Cory remarks to Shawn that it's their first fight ever. Cory and Topanga had several fights in the show prior to this. (00:12:50)
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)
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.