Continuity mistake: In the scene when Harold and Kumar go into the girl's bathroom and hide in the middle stall, you can see all of the stall doors are closed. When the twins are standing at the mirror in the bathroom, you can see in the mirror that the stall door behind the twin in pink is open, and then it is closed again. (00:23:45)
Revealing mistake: After they almost drive the Xtreme truck off of the cliff, Kumar gives a speech on their ancestors. He appears to be standing too far in front of the vehicle, which is partially over the cliff. In some shots in the same scene we see him standing on a short outcropping, but the angle of him to the vehicle doesn't match with the earlier shots.
Continuity mistake: As we see Harold and Kumar in the car we see a close up shot of Harold on his laptop. We also see a USB wire in the side USB port to which is attached a small light set off to the left of the screen. In one of the wide shots this light can be seen, but in all the others it has disappeared.Scrappy
Continuity mistake: Harold's Toyota Camry changes between shots a few different times in the movie. In the beginning and for the majority of the movie, the Camry is one of the more expensive trim levels with alloy rims. During some of the shots, it switches back and forth from this to a base model Camry with wheel covers. One of the times this happens is when they are wrestling with the raccoon.
Continuity mistake: When Harold and Kumar pull up into the Burger Shack drive-through, the guy goes crazy, saying, "Let's burn this muthaf*cka down.", he then knocks over the rack in the back, and all the stuff falls off of it. A few shots later, the rack is upright again and all the stuff is back on the rack.