"The full-frontal nudity? I thought that was hilarious," Segel, who played Peter Bretter in the film, explains. "I was actually not very uncomfortable doing it. I really felt free. You have to put it in the context that this was 2006, 2007, and this hadn't been done before, in my recollection, where the main guy was going to be naked in the first five minutes of the movie."
Segel says that "it wasn't just for shock value" -- there was "a creative idea behind it."
"I wanted it to be the most humiliating breakup of all time," he says of Peter and Sarah Marshall's (played by Kristen Bell) relationship. "When I was writing it, I thought to myself, 'The problem with romantic comedies is, you know what's going to happen. The guy on the poster is going to end up with the girl on the poster. But if I open this movie with something you cannot believe you're seeing, you're sort of forced to go into a different attitude. You don't know what's going to happen in this movie.'"
"We tried to carry that all the way through to the puppet musical," he continues. "We wanted it to have the feeling of a romantic comedy, but to be completely unexpected. It's pretty fearless."
Segel isn't the only one who's discussed full frontal scenes in interviews this year.
In January, Jamie Dornan told GQ UK that even though he avoided going full frontal for Fifty Shades of Grey, shooting the S&M scenes on set was still embarrassing.
"Your dignity is intact as much as it's all tucked away in a little flesh-colored bag," he told the British men's magazine. "As a guy you put all your essentials in a little bag and you tie it up like a little bag of grapes and it's tucked away. It's quite a peculiar thing to do every day."
Charlie Hunnam -- who was originally cast to play the lead role of Christian Grey in the erotic romance flick -- talked nudity with ELLE Canada in March, revealing that he doesn't have anything to hide.
"The level of nudity that I do now, which is taking my shirt off, doesn't bother me at all. But I have done full frontal before," the Sons of Anarchy star explained. "I did full frontal when I was 18 on the TV show Queer as Folk. But because I was playing a 15-year-old character, the censorship people wouldn't allow us to put it on TV."
"I think when I was young, I was a little bit more fearless with that stuff," Hunnam continued. "I don't know...I'm sure I would; I have nothing to hide."
We've seen plenty of celebs strip down this year (some intentional, some not!) -- from Khloe Kardashian to Justin Bieber. Watch the video below to see the stars that left little to the imagination in 2015.