Plot hole: In the start of season 4 we meet Liberty's little brother, Danny. J.T. and Manny are making fun of him because he is new to the school and is starting out. If he is starting out, then he should be in the 7th grade, because it is stated in the first episode that the school changed into a 7-12. Liberty, J.T., Manny, Emma,Toby etc. are all in the 10th grade so how does it end up that Danny is a grade below Liberty?
Other mistake: In the episode "The Mating Game," Ashley states, "Terry, sorry about last night." Unless she was with Jimmy and Ashley, because she is referring to when Ashley yelled at Terry. But that was 2 days ago, so why is she saying "last night" when it was 2 days ago?
Plot hole: Emma is getting people to sign a petition to get tampon machines in the girls' bathroom. But in the episode "Mother & Child Reunion," when Joey and Caitlin are in there, there's a tampon machine. So you can see that they took it out or just neglected the fact to support the plot of this episode.
Other mistake: When Zoey watches the assault video of her, when Luke or Neil put their hand down on Zoey's leg, a few milliseconds before that there is another left hand, wearing a watch, but that can't be Neil's hand either because his other hand is right on Zoey, and so is his body.
Continuity mistake: When Craig has to decide weather to go to college or stay with his band, he has to fill out an exception letter. When he is writing his name you can see there is nothing else on the paper, but when he picks it up it suddenly has a bunch of writing.
Continuity mistake: When Miles and Winston are entering the house to confront Frankie, if you look on the ground you can see wet pool footprints, but nobody was in the pool. A bit later on when Frankie goes in the pool there are more wet pool footprints, which must be from previous takes.
Continuity mistake: When Emma, Mr. Simpson, and Spike are sitting at the table eating Chinese food, Emma is already using the chopsticks when Mr. Simpson asks her, "What plans do you have for the weekend? Any hot dates?" Emma breaks open the set of chopsticks she was already using before she replies, "No, Mr.Simpson."