A Very Topanga Christmas - S5-E11
Continuity mistake: When Topanga tries the egg nog, you can tell that there is nothing in the paper cup.
A Very Topanga Christmas - S5-E11
Character mistake: When Cory is talking to Alan in the middle of the night, he mentions that Topanga has been staying with them for less than 8 hours. She arrived during the day time, and then convinced the family to go to Vermont to get a real Christmas tree, which they are cutting down at nighttime, and Eric later expressing after the new tree has been put up and decorated that it was 600 miles round-trip. All of this would take more than 8 hours. Driving from Philadelphia to the southernmost part of Vermont and back again alone would take more than 8 hours.
A Very Topanga Christmas - S5-E11
Other mistake: When Topanga knocks on Cory's door at 3:00 AM, he comes out and expresses that he's always asleep at this time of night. Despite this, he shows no signs of having just been awakened from his sleep. On the contrary, he appears very alert.
A Very Topanga Christmas - S5-E11
Factual error: This episode takes place near and on Christmas, but an establishing shot of the Matthews' house early in the episode shows the trees to still have very green leaves, and outdoor plants and the front lawn are still alive and healthy looking. None of this is possible in winter in Philadelphia.
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.