It's been 20 years since "Cruel Intentions" hit theaters and exposed moviegoers to the seedy, sexual underbelly of New York City prep school life. And despite middling reviews at the time, its popularity has endured over the years. Let's celebrate the occasion with a few behind-the-scenes secrets about this steamy drama.

1. The original title for the film was "Cruel Inventions," but it was altered after test audiences complained that it sounded like a science fiction movie.

2. "Cruel Intentions" is actually a modernized adaptation of French author  Pierre Choderlos de Laclos' 1782 novel "Les Liaisons dangereuses."

3. That novel has been adapted for film six other times, most notably 1988's "Dangerous Liaisons."

4. Producer Neal H. Moritz previously worked with Sarah Michelle Gellar and Ryan Phillippe on 1997's "I Know What You Did Last Summer" and immediately made them his top choices to star in "Cruel Intentions."

5.Reese Witherspoon improvised the memorable moment where her character Annette slaps Phillippe's Sebastian. That's why Phillippe's expression of shock is so genuine.

6. Despite both playing high schoolers in the film, Witherspoon is actually five years older than Gellar.

7. Costume designer Denise Wingate purposely clothed Annette in light colors and Sebastian in dark colors in order to contrast their opposing natures.

8. While Kathryn tells Sean Patrick Thomas' Ronald that Sebastian hit her, the film doesn't reveal whether she's actually telling the truth. Director Roger Kumble filmed a scene of Sebastian hitting Kathryn but chose to remove it and maintain the ambiguity.

9. An earlier screenplay draft featured an alternate ending where Annette chooses to withhold the journal and blackmail Kathryn rather than publishing it.

10. There are currently two direct-to-video sequels to "Cruel Intentions," though 2001's "Cruel Intentions II" is actually a prequel and 2004's "Cruel Intentions 3" is a loosely connected spinoff.

11. "Cruel Intentions 2" was created using footage from three episodes of an unaired TV series called "Manchester Prep," and follows younger versions of Sebastian and Kathryn.

12. In 2015, NBC announced plans for a sequel TV series that would feature Gellar reprising her role as an older Kathryn and revolve around Sebastian and Annette's son.  Unfortunately, NBC eventually scrapped the project the following year.