In the scene where Matt is driving at the gun range, he looks at the camera and imitates the exact same hand gesture Dylan Klebold, one of the two gunmen in the Columbine School shooting of 1999, was videotaped doing while driving to school.
In the scene when Matt and Owen are talking to the boys in the park, they actually met them in the park. With the help of Kevin Smith, they tracked down the kids and added their film as a DVD extension.
You can hear the seagull sounds Matt records early in the film later throughout the film.
The yellow t-shirt with the black bull that Matt wears walking through the hallway during the Best Coast montage is the same t-shirt that the character John wears during Gus Van Sant's Elefante (2003), which is based on the Columbine School shooting.