Brand stars in the film "Get Him to the Greek," which opens Friday, and is engaged to pop singer Katy Perry. The Judd Apatow-produced comedy, which stars funny man Jonah Hill and Sean "Diddy" Combs, has Brand reprising his character from 2008's "Forgetting Sarah Marshall," the British rock star Aldous Snow.

"It's a lot of hard work pretending to be a rock star, but it went really, really well and it's good," Brand said in a phone interview Wednesday. "It was like doing karaoke but everyone's backing me up and telling me I'm good and laughing."

Brand's character is the lead singer of the fictional band Infant Sorrow, which performs on the film's soundtrack, also out this week. That's not the only place the British entertainer will sing a tune -- he may perform a duet with his fiancee at their wedding.

"I think it should be `Monster Mash,'" he said of the classic novelty song. "Something that sounds either sweet or funny." As for Perry's bachelorette party to be thrown by Rihanna, Brand said: "I'll imagine it will be wild. She knows how to party." The two have not set a wedding date.

In the last few years, Brand says he's grown a lot.

"Getting off of drugs is a big change and then there's another big transition when I stopped," he said. "And the lifestyle before I was in a relationship, that was a big change also. That was a mental time." Brand, who is known for his wild roles and raunchy comedy, says he's interested in directing films and playing more serious characters.