Revealing mistake: When Jen and CJ are talking at Boston Bay University, and CJ mentions 'The Stand'; Jen suddenly gets up to leave thinking he is referring to religion. As she turns to walk away; you can see for a brief moment the real tattoo on the lower back of Michelle Williams, in the slight gap between her shirt and pants.
Visible crew/equipment: During Joey's surprise Birthday party in her dorm room, she and Dawson start arguing and everyone else suddenly leaves. Right after that, as Joey and Dawson are standing in the room arguing, you can see the shadow of another person on the wall just behind Joey, to the left. The shadow appears to be a boom operator, with a long-handled boom mic, and you can see him moving in and out of the shot by his shadow. Dawson and Joey aren't moving at this point, so neither of them could be causing the shadow. Also, there is equipment shown in shadow as well.
Factual error: Towards the end of the episode when Joey and Dawson are arguing about their relationship, Joey makes a statement that "Dawson bought the Champagne" referring to their romantic time on the movie set earlier that evening. However, when they were having that drink on the porch of 'Dawson's House' on the movie set; Dawson explained to Joey that the Champagne was from a free gift basket, one of many given to Directors before they start production on a new film. Therefore, Dawson never bought the Champagne, he simply stole it from the gift basket.