Continuity mistake: When Mr. Feeny says "As if you are returning for your 20th high school reunion", there is a red crown on Mr. Feeny's desk with Minkus sitting on a chair at the end. After the camera cuts to a close up of Minkus saying 'More like a pre-union", there is a cut to Mr Feeny who turns to him. Minkus is all of a sudden holding the crown on his lap, then he is seen putting the crown back onto the desk.
Plot hole: After Shawn leaves Cory's house to get a pizza, he calls Cory on the phone literally a minute later to tell him that Lenny Dykstra is at the pizza place. There's no way Shawn could have left Cory's house, walked to the pizza place, spotted Dykstra and either asked to use the restaurant's phone or found a pay phone to call Cory in such a short amount of time.
Continuity mistake: When Alan is talking to Cory in his room, telling him that he can always come home, he is pointing his finger at him. He has his right arm rested on his legs and is pointing with the left arm. Just before the shot changes to face Cory, Alan stops pointing. In the next shot, facing Cory, Alan has his left arm resting, and is pointing with his right arm.