When Tad kisses Carmen he has her face in both hands, then after the cut he only has his right hand on her chin.
Veronica drops her LeBaron off at Weevil's uncle's shop to be fixed. But later that day, when she takes the pictures of Tad and Seth at the boardwalk, she is sitting in her LeBaron. Then the next day, Logan brings her car to her, saying he had someone pick it up from the shop that day.
In season one it is said that Shelly Promroy's party was on Dec. 7, 2003. In season three Veronica tells Parker the party was an "end of the year bash, summer 2004".
After Carmen (Natalia Baron) smashes the phone in the Mars Investigations office, Veronica (Kristen Bell) gets an Instant Message. Her email program indicates that she is working offline however. She could not have received an IM.
When Carmen (Natalia Baron) and Veronica (Kristen Bell) are making the phone call so Tad (Jeff D'Agostino) can 'tie his own noose', Veronica hands Carmen the phone with no connection to her laptop. When the scene cuts to Carmen on the phone with Tad, the phone clearly has a cable connecting it to Veronica's computer.
When Veronica (Kristen Bell) & Logan (Jason Dohring) are kissing in the bathroom, reflection of the dolly (a device on which cameras manoeuvre) can be seen in the reflective surface of the towel dispenser.
(at around 1 min) As Kristen Bell is getting out of the car, her shirt rides up and exposes a wireless microphone pack in the small of her back.
(at around 1 min) When Veronica and Logan are talking in front of the fireplace, you can see the boom mic reflected in the mirror above the mantle, going back and forth between them as they say their lines.