1. Jason Segel actually got naked-dumped in real life. Universal "The whole time I'm thinking this is really, really funny," Segel said. "I'm going to use this in a movie someday. And slowly her voice became like the teacher from Charlie Brown, you know, just wha-wha-wha, wha-wha-wha, while I was slowly constructing the scene in my mind. 2. IRL, though, Segel actually put clothes on midway through the breakup...which was equally awkward. Universal "Picking out an outfit for the second half of a breakup is the hardest outfit you'll ever pick in your life," Segel said. 3. Jason Segel didn't tell his family about the nude scene; his mother cried in the theater. Universal Segel didn't tell her about it as a "joke," but apparently she didn't find it very funny. She also sent out an email to family members warning them about the scene, but saying it was "essential to the plot." 4. Although Segel did his own nudity, those aren't actually Mila Kunis' boobs in the photo. Universal Judd Apatow confirmed that the photo Peter valiantly removes from the men's restroom was Photoshopped. 5. Years before Forgetting Sarah Marshall, Segel had actually written a Dracula musical that he wanted to perform, with puppets. Universal The first person he played the musical for was Judd Apatow, who told him, "You can't play this for anyone, ever." 6. Later, Segel jokingly suggested they use the musical in the movie, but Judd Apatow liked the idea. Kevin Winter / Getty Images The two wanted an idea that was different from the usual romantic-comedy ending, and they felt that the Dracula musical would be sufficiently unique. 7. Russell Brand hadn't even read the script when he came in to audition. Universal According to Segel, Brand walked into the room and said he had "given a cursory glance" at the script, and asked what it was about. 8. Based on Brand's attitude, Segel completely re-wrote the character of Aldous Snow. Universal Originally, the character was supposed to be more "posh" and refined. Charlie Hunnam was rumored to be in consideration for the role. However, upon seeing Brand's audition, Segel changed the role entirely to fit him. Interestingly, Rhys Ifans' character in Segel and director Nicholas Stoller's follow-up, The Five-Year Engagement, sounds a lot like the original version of Aldous. 9. Kristen Bell was actually in a movie about killer phones, but Segel and Nicholas Stoller weren't aware of it. Universal They had written the scene where Peter and Aldous mock Sarah's film about killer cell phones before they knew that Bell had actually starred in an actual one. 10. That wasn't the only strange coincidence: Bell's show, Veronica Mars, was cancelled the day before Bell shot the scene where Sarah finds out her show is cancelled. Universal So in that scene, Bell could very easily pull from real-life experiences. 11. Segel got the idea for Crime Scene: Scene of the Crime after he guest-starred on CSI. Universal He found the "seriousness" of it very funny, and decided to parody that in the movie. 12. Mila Kunis auditioned for the lead in Knocked Up, but didn't get the part. Universal Thus, Apatow made sure she was in consideration for Sarah Marshall. 13. Segel wrote the song "Inside of You" as an attempt at "the worst song your ex-girlfriend's new boyfriend could sing in front of you." Universal Mission accomplished. 14. Actual women named Sarah Marshall were upset by the billboards, which had mean messages addressed to Sarah's character. ihatesarahmarshall.com That includes a 70-year-old woman in New York, who said the language was "a bit too rough for my taste." 15. Segel's breakup with Freaks & Geeks co-star Linda Cardellini partially inspired the movie. Universal Segel noted that the movie is inspired by multiple breakups of his, though, and Cardellini wasn't the one who dumped him while he was naked. 16. The puppets for the Dracula musical were made by Jim Henson's Creature Shop. Universal This, along with Peter singing the Muppet Show theme song, are two instances of foreshadowing that Segel would later go on to write and star in the rebooted Muppets movie.