When Lorelai is on her cell phone at the diner, she throws food at Luke, leaving a stain on his back. The stain appears, disappears, and reappears throughout the scene - before she throws it.
Lorelai's white collar changes from slightly tucked in on her left to fully exposed while inviting Luke to movie night in the diner.
when Rory is talking to Tana about what to wear for her date, you can tell when she says "go back to your leg" that the audio is changed from something else.
When Lorelai is getting back in her car after not wanting to go to the Friday night dinner without Rory, when she opens her car door the studio light is reflected in her car window.
When Rory and Lorelai are talking about dating, Rory tells her mom that she hasn't dated either. However, Lorelai went on a date with Paul, her classmate from business school, she went out with Peyton, the man she met at the auction, and also Alex, who she met through Sookie and went on a trip with to New York.
When Rory is on her date, her date asks her if she has any siblings, and she answers "No." This is not true, Rory does have a half-sister, born in Dear Emily and Richard (2003).