Justin Timberlake talks Lady Gaga, Mila Kunis, and involuntary noises

Justin Timberlake may have turned 30 this year, but he certainly hasn't lost any of his boyish charm. On "The Tonight Show" he told Jay Leno that the biggest change in his life since hitting the big 3-0 is... well, noises.

"I'm finding more and more that I have these involuntary noises that just come out of me," he says. "It's very specific, actually. It's when I'm sitting down or when I'm trying to get up from sitting down. It's like a thing now. I actually inhale air and this random noise comes out of me like I think that I'm ingesting helium or something and it's going to actually lift me off the seat."

His upcoming movie, "Friends With Benefits," is  "heartwarming film," as he says. Well, not that heartwarming. "Yeah, there's a lot of sex in it, it's called 'Friends With Benefits,' Jay."

Despite his playful relationship with Mila Kunis, which we saw on stage at the MTV Movie Awards, Timberlake says they weren't comfortable with their sex scenes at first. "We'd never really met each other before we started working on the film," he says. They actually adjusted the shooting schedule to film the two weeks' worth of love scenes at the end of the filming so that Timberlake and Kunis could develop a "rhythm" first.

Timberlake's "Bad Teacher" opens this weekend and he just came off a year of heavy promotion for "The Social Network," so he says that this year, he plans to take a well-deserved break. "I mean, to be honest, seriously, I'm 30 years old and two thirds of those years I've worked a lot. You get to a point where you're like, 'Why am I doing all of these things at the same time?'"

Watch the first part of the interview below to catch a shocking revelation about Lady Gaga's "Saturday Night Live" birth, and plenty more from Timberlake.