A lot of the filming was done at the high school in Lockhart, Texas. The football team was used and the city was told to show up for the football game and were given fake t-shirts to wear in the stands.
Near the end, Marybeth refuses to take the alien drug test by saying she's allergic. Jordana Brewster's character Delilah says, "Yeah, and I'm Portuguese." In real life, Brewster can speak fluent Portuguese.
In exchange for product placement in this film for clothier Tommy Hilfiger's fashion line, the teens from the movie's cast appeared together in a TV commercial & print ad campaign for Tommy Jeans throughout 1998.
Elijah Wood, Clea DuVall, Jordana Brewster and Shawn Hatosy appear in the music video for "Another Brick in the Wall, part 2", performed by the Class of '99, which is featured in the film's soundtrack. In keeping with her character Stokley, Clea DuVall does not lip sync the lyrics with her co-stars.
In a scene where students are being called to the principal's office, one name called is Thomas Nix. In reality, Tommy Nix is one of director Robert Rodriguez's friends from college. He helped Rodriguez write his second feature Roadracers (1994).
The girl student with the black top and tan skirt who laughs at Elijah Wood getting his balls smashed into a flagpole was Austin rocker Sarah Talbot, who at the time was the front woman for The Hollywood Wife Beaters. Laughing at Wood was her idea and the director kept it in.
Among the motivational banners in the school's locker room is a sign that says "The will to win comes from within" which is particularly appropriate considering the body snatcher nature of the alien invaders taking over the staff and student body.
Harry Jay Knowles:
The bespectacled, red-haired teacher having his injury examined by Nurse Harper (Salma Hayek). Knowles, most famous for his movie news website "Ain't it Cool News," is a long time friend of Robert Rodriguez and a fellow resident of Austin, Texas, where this movie was filmed.