(at around 23 mins) When Jesse and Chester are taking out the trash in their girlfriends home, Chester takes off his left shoe and sock but then picks up the bottle top with his bare right foot.
When Mr. Pizzacoli walks into Jesse and Chester's house, out the window there is a driveway, but when they leave their house, there is no driveway. This also happens when the twins come over to break up with them.
(at around 23 mins) When Jesse and Chester are taking out the trash in their girlfriends home, Jesse takes off one shoe and Chester takes off one shoe and sock but directly after when they drop the trash, you can see they both have their footwear back on, and in the next shot, when thrown outside their footwear is off again.
(at around 33 mins) When Tania the transsexual stripper talks to Jesse and Chester the road in the background is dry, when the cops pull up the ground is wet. It's true that cinematographers love wet roads, but there has been no rain.
(at around 22 mins) When Jesse and Chester are taking out the trash in their girlfriends home, the cap on the top of the white bag bounces away. In the next shot, it glides from the bag.
(at around 22 mins) When the guys are taking out the 'trash', polystyrene chips can clearly be seen through the white bin bag, showing what the bags are filled with.
(at around 1h 3 mins) There is a hand putting items in the locker at Captain Stus.
(at around 30 mins) When Jesse and Chester make out, "The Little Things" by Good Charlotte is played. The subtitles for it reads "dames" while they're actually saying "things".
(at around 56 mins) A cameraman is reflected in the windshield mirror of the car while Chester and Jesse hide from the ostriches.