AUSTIN – SXSW has turned into a launching pad for big Hollywood comedies over the past few years. Knocked Up (2007) and Forgetting Sarah Marshall (2008) had their debuts here, and this year Observe and Report and I Love You Man are on the bill.

The cast of I Love You Man gathered Saturday afternoon to discuss the film, which served as the opening night feature. The movie stars Paul Rudd, who is about to marry Zooey (Rashida Jones) but needs to find someone to be his best man since he is low on guy friends. Jason Segel stars as is potential buddy while Jamie Pressly and Jon Favreau play a bickering couple who provide a bit of a preview of what marriage could be like.

A large portion of Saturday’s discussion centered on improvisation during filming.

“I feel like I wrote the script, but everybody wrote the movie,” said the film’s director, John Hamburg. “Everyone got the tone of what we were trying to do, and then we just went and played around all day.”

Apparently, though, freedom to try new things has its limits, according to Segel.

“One time John screamed at me from off camera, ‘Oh, come on Segel! Just do it like a normal human being!'”

Fittingly, improv was the order of the day as the panel began. Technical problems were getting in the way of showing the trailer for the film to the audience. As the computer was being attended to, Rudd suggested that since everyone in the trailer was in the room, “We can just get up and do it if that makes sense.”

When the video finally played, the audio was somehow missing. But being the improvisers that they are, the cast filled in their voices, Mystery Science Theater 3000 style. The trailer might have been funny, but I’m happier that I got to see the live-audio version.