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: In this episode Cory has a full length locker, but in the previous episode (Hometown Hero) He has the top locker. It's always in the same stop, so there is no way that he changed lockers.
Continuity mistake: When Mr. Feeny says "As if you are returning for your 20th high school reunion", there is a red crown on Mr. Feeny's desk with Minkus sitting on a chair at the end. After the camera cuts to a close up of Minkus saying 'More like a pre-union", there is a cut to Mr Feeny who turns to him. Minkus is all of a sudden holding the crown on his lap, then he is seen putting the crown back onto the desk. (00:04:00)
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 Alan is talking to Cory in his room, telling him that he can always come home, he is pointing his finger at him. He has his right arm rested on his legs and is pointing with the left arm. Just before the shot changes to face Cory, Alan stops pointing. In the next shot, facing Cory, Alan has his left arm resting, and is pointing with his right arm.
The Grass is Always Greener - S3-E12
Continuity mistake: Early in the episode when Cory is talking to Shawn by their lockers, Shawn closes his locker and you can see one of the straps from his backpack sticking out on the bottom-right side of the locker. A few shots later, the strap is now sticking out on the bottom-left side. About a minute later in the scene, just before Topanga comes to talk to Cory, you can see the strap is now sticking out of the bottom-middle area.
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.
Revealing mistake: When Amy steps into the living room and sees Reginald, you can see a plain white wall behind the door that leads into the kitchen, when you should be able to see the kitchen itself, which would suggest another set was placed there and they didn't move it for the filming of this scene.
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.