Audio problem: When the waitresses are performing their song, you can tell they are lip syncing to a recording even though they are supposed to be giving a live performance. The vocals have a noticeable amount of reverb and are mixed evenly with the instrumental track despite the fact they aren't even using microphones. (00:06:49 - 00:09:00)
Everybody Loves Stuart - S6-E7
Audio problem: When Eric walks into Cory's hearing to the theme of "The People's Court," we find out the sound is coming from a tape player in his briefcase. When he opens up the briefcase and pulls out the tape player to stop it, the volume remains the same. The volume should have increased once he opened the briefcase. (00:14:30)
Graduation - S5-E24
Audio problem: When Mr. Feeny is reading off the names of all the graduates, you can hear reverb in his voice to indicate that he is speaking into a microphone. The problem is there is no microphone in front of him. You can see Eric holding the microphone next to him and singing into it, with no audio. If that microphone is turned off, then Feeny's voice should not be amplified. If the microphone is on, then we should also hear Eric as he is singing. (00:19:38 - 00:20:56)
The Thrilla' in Phila' - S2-E21
Audio problem: When Joey is saying "Frankie, tag me," his mouth movement is not synchronized with the dialogue.
Santa's Little Helper - S1-E10
Audio problem: When Amy is playing the piano with Morgan, the last few notes that they play while the camera is focused on them are out of sync. (00:19:50)
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.