When Joel (Jason Bateman) comes home from being punched at the bong session, he has a monster of a black eye. When he leaves the house the next morning, the shiner has completely vanished. (It reappears briefly, but in milder form, by the time he arrives at work.)
In the opening scene, the music store employees call the pickups on the Gibson guitar "humbuckings." Those type of pickups are either called "humbuckers" or "humbucking pickups," but not "humbuckings." Someone picky enough to fuss about the difference between "color" and "finish" would likely be the same way about pickups.
Early in the movie, when Cindy is sorting through her various forms of ID, an Ohio drivers license is shown. The issue date is April of 2001, with an expiration in April of 2010. An Ohio license must be renewed every four years.