Having seen the pilot so many, many times, certain bloopers/continuity errors always jump out at me. Like...
-When the police cruiser pulls out to pursue James and Donna ("What goes around comes around." "Around and around."), Harry turns the flashers/sirens on, but when you see a long shot of the cruiser pulling out, the lights on top aren't flashing.
-What high school has football practice in late February?
-The spelling of "Katherine" in the pilot opening credits.
-I know it's small town America, but Donna seems a little too trusting, seeing as she doesn't have a lock on her locker. She clicks it right open.
-Audrey's shockingly fast hair growth/make-over after the pilot - and likewise, Donna's between episodes 7 and 8.
-I realize that the intent was probably to help establish James as the resident "rebel without a cause," but his "Yo!" when his name is called in homeroom seems completely out-of-character for him.
-Lara Flynn Boyle does GREAT with her cry-acting in homeroom when she finds out that Laura is dead, but it's still fairly obvious to that there are no actual tears or waterworks happening there, just vocal sobbing.
-Slightly reminiscent of "24," I'm always impressed that Cooper managed to leave Philadelphia and arrive in Twin Peaks, WA within what seems like just an hour or two of Ronette having been found walking across the state line. Almost as if he knew from a dream that it was going to happen, so he left early that morning...
-During Cooper and Harry's stakeout at the Roadhouse (waiting for Donna to show up), we hear the opening bars of "Falling" and get a mastershot of...the Bookhouse, NOT the Roadhouse.
And don't even get me started on the Palmer and Hayward houses changing their appearance between the series and the film! Have people noticed others? I'm sure there must be quite a few throughout the series and the film...
(Keep in mind I'm not criticizing; I love the show and the movie dearly, the obsessive-compulsive in me just loves spotting those little inconsistencies for whatever reason.)