When Joey is picked up by A.J. and throughout their date, she is wearing a long skirt. At the end of the night, when she comes back home and is sitting outside with Dawson, her skirt becomes knee-length.
(at around 30 mins) Jen is catching up to Henry and causes her string on her sweater to catch her coat which shows through the scene, but when the camera cuts to a different angle, where the string is hanging down normally. The camera then cuts back to them walking again with her string caught on her clothes again until it falls off naturally.