When Paris arrives at Lorelai's house, she repeatedly asks Luke who he is and when Lorelai asks if they've met, they say no. They actually met before, when Rory was at Chilton and Paris came to the diner looking for a seedy story about Stars Hollow.
When Luke accepts Lorelai's proposal and the two wonder what to do next, Luke says "I don't know, this is new to me." Yet in episode 4.1 "Ballrooms and Biscotti" Luke admitted that he proposed to his girlfriend Nicole on the spur of the moment, and then immediately got married on a whim. Such a situation is certainly not new to him.
When Rory is unlocking the deadbolts she uses the same key for all the locks. However, in the previous episode Paris uses multiple keys to unlock them.
Lorelali has tan lines across her chest in the first scene that were not there at the end of the season 5 finale when she proposed to Luke.