Character mistake: At one point Cory is telling Shawn about how he can't protect Topanga and they've only been married for one week. But they spent their wedding night in jail, 12 days on their honeymoon and 1 night in their new apartment. So actually the couple have been married for 2 weeks.
For Love and Apartments - S7-E2
Character mistake: When Shawn is scolding Topanga for getting angry with Cory for travelling to Pittsburgh to try to get her parents back together, he mentions that he travelled a hundred miles to do so. Philadelphia is roughly 300 miles from Pittsburgh. Travelling only 100 miles westward from Philadelphia would barely get them past Hershey. (00:17:53)
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)
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.