Factual error: The car Flounder drives is a 1964 model, built beginning late in 1963, but the events of the movie take place in 1962.
Factual error: In the scene where Pinto buys/shoplifts food from the grocery store and meets the Mayor's daughter, the cash register has an LCD display. A little too futuristic for a flick set in '62.
Continuity mistake: In the scene where Otter and Boon are hitting golf balls near the ROTC drills, Otter puts down the golf bag he is carrying and draws a club. The camera moves to the ROTC trainees, and when it comes back to the golfers, the bag is back on Otter's shoulder and there is no club out of the bag.
Continuity mistake: In the scene where Otter is making out with Shelly from Dickinson college, in the back of the car she is clearly shown with her bra off, and it his hanging on her right arm by one strap. When the guys come running out of the club seconds later to make their escape, Shelly is shown jumping out of the car and diving through the window of the car parked next to it, but her bra is now on and hooked as if it hadn't been removed yet.
Continuity mistake: During the toga party, the mustard stain on Bloto's toga, disappears and reappears.
Revealing mistake: In the scene where the Mayor is giving his speech just before the parade begins, there is a man sitting in the bleachers behind him making bizarre faces and hilarious facial ticks in plain view of the camera.
Factual error: At Professor Jennings' place, the stoned Boon and Katy sing "Hey Paula." The song was only pressed in November 1962 and didn't break into the charts nationally until late December of that year, whereas the scene depicted takes place sometime in the autumn of the same year, before the song would've even been recorded.
Continuity mistake: When Flounder and Larry arrive at the Omega house for the party, sunlight can be seen coming through the windows, although it was night when they arrive.
Factual error: After trying unsuccessfully to call Katie at the all-night cafe, Boone questions where she could be at six in the morning. The scene occurs during broad daylight. If the time were accurate, this could not be so, since it occurred in November.