When Joey goes to see Pacey as he's vegetating on Doug's couch, the pillow he's lying on is covered with potato chip crumbs. When he lifts his head, his cheek is also covered with potato chips. Each time the camera shifts to Joey then back to Pacey, the number of chips on his face and pillow keeps changing. Once the pillow and his face are totally clean, then pan back and both are covered again.
After the first day of shooting Dawson's movie and he and Joey are lying on his bed discussing it, when the camera is on Joey, she's looking at Dawson with a thoughtful look on her face. But when the camera pans to Dawson, she's looking up at the ceiling, then pan back and she's intently looking at Dawson again.
When Joey goes to Paris, there is the flag of Canada, Quebec and Montreal visible on one shot.