Towards the end, when Turk is scraping gum off his windshield, first the top is down, and one second later it is up.
After the janitor has "gummed" Turk's Mini convertible, the top is open (as seen from a shot from inside the vehicle). Barely a second later, the top is completely closed.
Even though it's supposed to be Christmas, the time of year outside is obviously warmer. This can be seen when Turk is scrubbing gum off the car.
(at around 6 mins) When Cox mimes making a call on an old-fashioned telephone, his dialog "Hello? Operator? Give me..." is followed by overdubbed gibberish words which do not match what his mouth is speaking.