It's been 20 years since we were urged to "Choose Life" by junkie Renton (Ewan McGregor) in "Trainspotting," the bold Scottish indie that put him and director Danny Boyle on the map. American audiences had no idea what they were in for (toilet diving! babies crawling on the ceiling!) when it hit theaters on July 19, 1996.

In honor of the film's 20th anniversary this year, and with the long-awaited sequel finally happening, here's 30 things you might know about this cult film:

1. "Trainspotting" was a play before it was a film. Main character Renton was played by Ewen Bremner, who was cast as Spud in the movie. Bremner says he almost passed on the role of a lifetime: "Having played Renton onstage, I was a bit aggrieved not to be considered for the role in the film. I was just being a stupid snob. But I'm so pleased to have done it and I still love it."

2. Ewan McGregor, who had already starred in Boyle's first film, "Shallow Grave," was the first and only choice to play Renton.
3. McGregor's "Shallow Grave" costar, the future Doctor Who Christopher Eccleston, was offered the role of Begbie, but opted to film "Jude" with Kate Winslet instead. The part instead went to Robert Carlyle, who had previously starred as a homeless ex-con in "Riff-Raff" and a guy in love with a closeted man of the cloth in "Priest."

4. Boyle described his audition with Kevin McKidd, who had previously been in "Small Faces" as "like meeting one of the Beach Boys at the height of their fame -- the perfect picture of innocence." In other words, perfect to play clean-cut, Iggy Pop-loving Tommy.
5,Jonny Lee Miller was suggested for the role of Sick Boy by McGregor: "He just walked in and he was Sick Boy straight away, he was lolling about in his chair right in front of us," Boyle told Empire. He was the only non-Scot in the cast.

6.Kelly Macdonald (below, who made her debut in the film), still has the flyer asking for girls to audition for the film: "It said, 'Do you want to be the next Sharon Stone?'" I've still got it somewhere." She told The Scotsman she expected the audition to get her into drama school. "Then I kept getting called back. Drama school was out the window." The actress, who went on to star in "No Country For Old Men" and "Boardwalk Empire," never did formally study acting.
7. In 2009, Robert Carlyle told BAFTA that he played the riot-starting Begbie as a closeted gay man whose violent outbursts were due to his "fear of being outed." Irvine Welsh, who wrote the novel, agrees with that interpretation.

8. To play skinny heroin addict Renton, Ewan McGregor simply gave up alcohol and dairy for two months.
9. How did they film the infamous toilet scene? Cinematographer Brian Tufano says it was, "quite easy to shoot, once you've been inventive about it. We ended up cutting a toilet in half and putting a wooden chute behind it. Then, using an art technique called trompe l'oeil, and the right positioning of the toilet, we made it look like Ewan was going down the toilet."

"Then I suggested to Danny that as he was going down, Ewan's feet -- if he just twisted them, people might think he's just gone round the bend in the toilet." As for the "beautiful lagoon" he ends up in, it was a swimming pool in Glasgow. "People still talk about it. If you see someone going down a toilet, it's bound to stick in the memory."

10. The opening scene in which Renton is run over by a car takes about five seconds, but it required 20 takes. During breaks, McGregor had to be patched up by the on-set nurse, according to Empire's 1996 behind-the-scenes article.
11. Don't worry: No animals were hurt in the making of this film. The scene where Renton and Sick Boy shoot a dog in a park with a BB gun? Director Danny Boyle just yelled at it offscreen to get its startled reaction.

12. Although there is a scene where Renton, Sick Boy, Spud, and Tommy go out to the countryside and hang around the train tracks, they're not the "trainspotters" referenced in the film. In the novel, Begbie and Renton meet "an auld drunkard' at the Leith Central railway station. The man, who turns out to be Begbie's estranged father, asks them if they are "trainspottin'."
13. Jonny Lee Miller's James Bond-obsessed Sick Boy actually has a real connection to the spy series: His grandfather, Bernard Lee, played "M" in the Bond films until 1979.

14. Kelly Macdonald iinvited her mother and brother to the set while filming her sex scene with Ewan McGregor. D'oh! That scene actually had to be trimmed for the American release by a few seconds, mainly because it appeared that her character (who was only supposed to be 15) seemed to be enjoying it too much.15. Miller himself was once rumored to take over as Bond, and would have loved the job, but the one time he met one of the Bond film producers, he probably didn't make the best impression. "I had dinner with Barbara Broccoli, but there were a lot of other people at the dinner. At the time, I think I had a huge beard or mustache, which probably didn't do me any favors, you know? I didn't look exactly suave," he said in 2009.

16. Some of the cameos you might have missed: Author Irvine Welsh as Mikey Forrester, who sells Renton some ill-fated suppositories; screenwriter John Hodge, as the store security officer chasing Renton in the opening scene; and that's producer Andrew Macdonald as a prospective buyer of the "Victorian Townhouse" that a temporarily clean Renton shows him in London.17. Kevin McKidd (third from left), who currently stars on "Grey's Anatomy," admitted that the movie wasn't the big break for his career that it was for some of the other actors (possibly because he was on holiday when the promo photos were being shot, so he's not on any of the posters): "I had quite a lot of lean years after 'Trainspotting.' I did a lot of cool work but very low budget and very indie stuff. I think it was 'Rome' that was the game changer for me."

18. UK ads for the film were featured heavily at (where else?) train stations. PolyGram's marketing manager, Julia Short, told Empire in 1996, "PolyGram owns about eight poster sites at British Rail stations across the country, so we're putting up 'Trainspotting' posters, which we think is quite appropriate." One, at Charing Cross underground station in London, was 100 feet long.19.Paul Thomas Anderson was a huge fan of the film and tried to cast Bremner (left) in "Boogie Nights," a movie the actor now regrets turning down. "I never returned (director] Paul Thomas Anderson's calls. His people would be like: 'Paul really loves you, there's a great part here for you.' But I thought the script was too sentimental. Of course, when I saw the film I was kicking myself."

20. While wrapping "Trainspotting," Boyle (below, center) and producer Andrew MacDonald were in talks to take on "Alien: Resurrection," which ended up being directed by Jean-Pierre Jeunet.
21. McGregor and Boyle had a big falling-out after Boyle -– who had cast McGregor in his first three films -– went with Leonardo DiCaprio as his leading man for "The Beach."

The "Trainspotting" sequel marks the first time they've worked together since 1997's "A Life Less Ordinary." Says McGregor, "I miss working with Danny, I did some of my best work with him and he's one of my favorite directors I've worked with. There was some bad blood and ill feeling, but that's all gone now."

22. McGregor considers it his most important film, even bigger than "Star Wars": In a 2011 interview, he said, "it's still the main thing people ask me about when they come up to me in the street. I really get a sense that it's possibly the biggest film I've done, or definitely the most successful in terms of being in the human consciousness."
23. The writing on the wall of the Volcano Nightclub (where Renton meets Diane) is the same as that in the Moloko bar in Stanley Kubrick's "A Clockwork Orange," a movie Boyle encouraged the cast to watch before filming.

24. McGregor and Bremner have worked together quite a lot since "Trainspotting," including "Black Hawk Down" in 2001, "Perfect Sense" in 2011, and "Jack the Giant Slayer" in 2013. And of course, they'll both be in the "Trainspotting" sequel, due in February 2017.