Continuity mistake: When Roger is drunk and getting into bed, his alarm clock changes from 11:39 back to 11:38.
Continuity mistake: When the class go paintballing in the forest, Roger has a yellow paint splat on the back of his right shoulder. But when he hits Letcher with the paintball gun, the splat has disappeared.
Continuity mistake: In the scene where Roger is waiting for Amanda at the top of the escalator at the airport, the bundle of flowers in his hands changes position every time there is a shot of him. Sometimes you can see the bright red flowers, sometimes you can't. He is not moving the bundle around, simply holding it. (01:29:30 - 01:30:30)
Continuity mistake: When David Cross and John Heder are discussing how well John has been doing in the class, David's hot dog goes from having a bite out of it, to being whole again. (00:50:00)
Revealing mistake: Near the end of the film when Amanda and Dr. P almost take off together, there is a shot of them boarding. Look to the top right corner of the screen and for just a split second, you can see a glimpse of Roger chasing after them, along with Amanda's facial expression turn shocked. I'm pretty sure this happens because in the alternate ending Roger caught them when they were boarding.
Continuity mistake: When Roger is waiting for Amanda at the top of the escalator at the airport, he is holding a bouquet of flowers and the plane tickets. The ticket positions change from behind the flowers to in front or no tickets at all. He then runs towards another gate while holding his cell phone in his right hand and the tickets and flowers in the left. When he gets to the scanners, he is holding the tickets and flowers in his right hand but no cell phone. He puts the flowers, tickets, and shoes on the scanner and passes through. The flowers and shoes are seen after being scanned but the tickets did not come out of the scanner. (01:23:50 - 01:26:00)
Factual error: An AED delivers an electric shock for a fraction of a second. It is not capable of producing a sustained current, as is depicted in the movie when Roger and Dr. P are being electrocuted.