- Completely Different Title:
- Argentina: Killers from Another Galaxy
- Germany: Space Invaders
- Portugal: SOS: Killer Clowns
- Cowboy BeBop at His Computer: The Dickies hadn't seen the movie when they wrote the theme song and didn't know anything about it besides the title, which is probably why the chorus is just the film's title.
- Dawson Casting: Mike and Debbie are supposed to be teens, yet are played by actors in their late 20s (although Dave does reference "your college friends" so they could be college students too). The college kids who get arrested look pretty old to be drinking in the park, given the punk's male pattern baldness.
- Deleted Role: The Joe Lombardo who Mike finds cocooned in the circus tent early on was supposed to feature in an opening scene; he's rejected by his date and drives off, before running into the Klowns and getting killed. This was scrapped when they decided to have an opening credits sequence first.
- Executive Meddling: The original script ending had Dave and the Terenzi brothers all being killed. The producers wanted something more "upbeat" and three different endings were shot. One had just Dave dying, another had just the Terenzi brothers dying, and the final version (the one they ended up using) had all of them living.
- Prop Recycling: The Chiodo Brothers repurposed the Clown masks for the trolls in Ernest Scared Stupid.
- Screwed by the Network: As stated on the main page, its acquisition by Disney blocked the creation of a sequel when Disney forbid Fox from proceeding with the project. Since Fox owns the rights to Killer Klowns but Disney has full control over Fox's production schedule, it seems unlikely that a Killer Klowns sequel will ever be made.
- Throw It In: In one scene, Slim causes a car accident by ramming into the side of a car and causing it to fall off a cliff and crash. This accident was supposed to be more spectacular, but the crew members however forgot to remove the stoppers under the wheels, so the car only tumbled off and got caught on a tree. That's what's shown in the film.
- What Could Have Been:
- The security guard the Klowns kill with pies was supposed to be played by Soupy Sales, who was known for being hit with pies on his television show, but the studio declined, believing no one would recognize him.
- A deleted scene would have Mike, Debbie and Dave beating up one of the Klowns in the finale.
- A deleted scene would've evoked the Tightrope Walking trope by having the protagonists encounter a passage where they must walk a tightrope in a fog; they manage, but wobble enough to show it's not easy, then when they reach the end of the passage, the rope is bent into steps which lead to the next doorway. It was deleted because hard to put on film with the limited budget and resources.
- The Wiki Rule: Amazingly enough, there is one.
Trivia / Killer Klowns from Outer Space