Donnie Darko infamously made just a little over $500,000 in its initial theatrical release during the fall of 2001. After word spread that there was a weird little sci-fi movie featuring Drew Barrymore and Patrick Swayze with an utterly confusing storyline that had viewers spending hours attempting to understand it, the film made more than $15 million in DVD sales. Here are 18 things you might not have known about the apocalyptic cult classic that helped to jumpstart Jake Gyllenhaal's career.

1. VINCE VAUGHN TURNED DOWN THE LEAD ROLE AFTER MEETING THE DIRECTOR FOUR TIMES.

In the film's DVD commentary, writer-director Richard Kelly explains how he had met with the then-31-year-old Swingers star a number of times, but Vaughn was uncomfortable with playing a 16-year-old. Mark Wahlberg was also supposedly interested, but only if he could play Donnie with a lisp.

2. JASON SCHWARTZMAN AGREED TO PLAY DONNIE.

He liked the script and was “attached” as the film's star, until scheduling conflicts ultimately forced him to back out.

3. DREW BARRYMORE SAVED THE DAY.

On the set of the movie Charlie’s Angels, Barrymore and Kelly agreed that her production company, Flower Films, would produce Donnie Darko for $4.5 million (and that Barrymore would play Ms. Pomeroy, a teacher). Kelly says that if Barrymore hadn't stepped in, the movie would have either gone straight to video or cable TV via Starz.

4. OSCAR-NOMINATED ACTRESSES MARY MCDONNELL AND KATHARINE ROSS WERE BOTH PAID SCALE.

They played Rose Darko and Dr. Thurman—Donnie's mother and therapist, respectively. McDonnell was so excited for the part that she got her first ever speeding ticket driving to the set.

5. IT WAS SETH ROGEN’S FIRST FILM.

He played the bully Ricky Danforth. Years later, he still didn’t understand the movie.

6. PATRICK SWAYZE WORE HIS REAL CLOTHES FROM THE 1980s.

Jim Cunningham’s Cunning Visions infomercials were even shot at Swayze’s ranch in Calabasas, California. When asked about working with the actor, Richard Kelly confirmed that, "He's the nicest guy ... He wanted to take a flame-thrower to his image. He was fearless. We shot the infomercials on his ranch. Those were his real clothes from the '80s. He frosted his hair specifically for the part. He totally got it and was so cool about it."

7. THEY GOT PERMISSION FROM THE CREATOR OF THE SMURFS TO TALK ABOUT SMURF SEX.

Initially Richard Kelly sought permission from the estate of Peyo, the Belgian creator of the diminutive blue creatures, to show a Smurf doll for Donnie and his friends to shoot at. While on the same conference call, Kelly was told that Donnie would also be allowed to talk about Smurf sex, because what had been written in the script was considered an accurate description.

8. KELLY CAME UP WITH THE IDEA FOR THE FUTURE BLOBS WHILE WATCHING FOOTBALL (NOT ENTIRELY SOBER).

Legendary football TV analyst John Madden used to use a "telestrator," where he'd diagram a paused video to show where the players were about to go moments before letting the tape roll. Kelly watched this while high and started to think about what would happen, hypothetically, if “someone upstairs” was doing that to humans.

9. U2 WAS RESPONSIBLE FOR THE HIT COVER OF "MAD WORLD."

Working with a small budget, composer Michael Andrews tried—and failed—to get the rights to U2’s “MLK” for the final scene in the movie. Instead, he got his friend Gary Jules to come in and record a cover of the Tears for Fears song “Mad World.” It was released as a single and reached the top of the U.K. charts in 2003.

10. DONNIE AND GRETCHEN WERE SUPPOSED TO SEE C.H.U.D.

But Kelly didn’t have enough time to wait the eight to 12 weeks it would take to find out if they could get the rights to the 1984 horror movie. Sam Raimi allowed his movie The Evil Dead to be used instead. Raimi coincidentally drove by the Santa Monica theater on the day they were shooting the scenes and saw his 1981 movie title up on the marquee.

11. JENA MALONE COULDN’T PRONOUNCE NOAH WYLE’S CHARACTER’S NAME CORRECTLY.

So Gyllenhaal, as Donnie, improvised and corrected Gretchen on how to pronounce Professor Monnitoff’s last name. It stayed in the movie.

12. NOAH WYLE DECIDED THAT PROFESSOR MONNITOFF WAS DIABETIC.

Which is why he eats candy in some scenes.

13. A LOT OF WRITERS HAVE SAID THAT "CELLAR DOOR" WAS A BEAUTIFUL COMBINATION OF WORDS.

Miss Pomeroy claimed that a “famous linguist” wrote that “cellar door” was the prettiest English phrase possible. The “famous linguist” could be one of many authors, according to a 2010 article in The New York Times. It was written in the 1903 Cyrus Lauron Hooper novel Gee-Boy that an Italian savant believed that cellar-door was the “most beautiful combination of English sounds.” In 1920, H.L. Mencken wrote that “cellar-door is musical.” Twelve years later, Dorothy Parker commented that she preferred “cellar door” to some of the words Wilfred J. Funk (President of Funk & Wagnalls) wrote were the most beautiful English words. J.R.R. Tolkien talked of cellar door’s “special beauty” in a 1955 speech. C.S. Lewis and Norman Mailer both wrote positively of “cellar door” in the 1960s.

14. KELLY LAUGHED SO HARD THAT HE WAS FORCED TO LEAVE THE SET.

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Beth Grant’s character speaking about how Donnie directed her to put a Lifeline exercise card in an uncomfortable place made the writer-director crack up. "They had to physically remove me from the set because I was messing up the takes I was laughing so hard," Kelly recounted. "To be able to laugh while you're working is the coolest thing in the world. It's the comedy that makes it fun, that makes it tolerable, that makes it the best that it can be."

15. DONNIE HAD FANTASIES OF ALYSSA MILANO.

At least according to the original script. For legal reasons, Donnie’s fantasies had to involve Christina Applegate instead.

16. IT TOOK 28 DAYS TO SHOOT.

Or as long as Donnie Darko had until the plane was going to crash. Kelly swore it was a coincidence.

17. THE DIRECTOR’S CUT GOT INTO A BIGGER SCI-FI EXPLANATION.

With an additional 21 minutes of footage, Kelly used more “science fiction logic” in the Director's Cut of the movie that much more strongly hints at Donnie’s telekinetic powers and his destiny to die. Also, the fat man in the tracksuit is an FAA employee spying on the Darko family, and the woman with the clipboard is a Star Search talent scout.

18. THERE WAS A SEQUEL ABOUT SAMANTHA DARKO.

In 2009, Daveigh Chase reprised her role as Donnie's sister, Samantha Darko, in S. Darko—a poorly reviewed sequel that was made without Kelly’s involvement. In 2005, Kelly made it clear that he would never shoot a sequel to Donnie Darko because it would “destroy its integrity.”

All images courtesy of Getty unless noted otherwise