Continuity mistake: After the fight scene Jonah Hill says ”hey when did I get stabbed?” and it shows his side view with a horn object in his back. But in the earlier shot when he broke the vase on the head of the kid who he was fighting, everyones cheers and the camera shows his side view and there is no horn in his back.
Plot hole: In the first arrest scene Jenko (played by Channing Tatum) fails to read the suspect his Miranda Rights and the suspect is later released because of this. Miranda Rights are not read upon arrest nor do they have to be unless the arresting officer is questioning the suspect about an offense. Miranda Rights are more often read during an interview if the crime is that serious but in this instance (possession of controlled substances) the suspect would have most likely been handed over to a patrol unit with a vehicle and taken to jail without being questioned, at least by the arresting officers.