Continuity mistake: At the end of the movie when everyone is in Wayne's basement, we see Benjamin painfully walk up to Wayne's house for each ending in the dark. When the scene changes to Wayne's basement for the first ending, you can see through the basement window directly behind them that it's broad daylight. This is especially easy to see when the equipment starts to spark.
Continuity mistake: When Wayne and Garth are on their way to the Alice Cooper concert they show the car from behind you can clearly see that Garth is driving and Wayne is in the passenger seat but when they cut back to the car from inside Wayne is driving and Garth is in the passenger seat.
Trivia: The police officer in Stan Makita's Donut Shop is named Koharski, in reference to NHL Referee Don Koharksi. After poorly officiating game 3 of the 1988 playoff series between the Devils and Bruins, Devils coach Jim Shoenfeld and Koharsky argued on the way to the dressing rooms. Koharsky fell and told Shoenfeld he'd be suspended for pushing him, and that it was all on film. Shoenfeld said, "Good, cause you tripped and fell you fat pig, have another donut.". All this was shown on ESPN.
Trivia: When Wayne plays "Stairway To Heaven" in the music shop, he is then stopped and says "No stairway". The filmmakers actually tried to get the song played in the movie but were denied, so this is just a little nudge at them in this scene. I think Mike Myers mentions this on the commentary on the DVD.