WATCH: Justin Timberlake and Mila Kunis Settle the 'Friends With Benefits' Debate

Last night's 'Friends With Benefits' premiere in New York turned out to be a celeb fest with the film's A-list stars all showing up, and ET was there to ask movie leads Justin Timberlake and Mila Kunis if  being "friends with benefits" can really work out in the long run.

"It certainly makes for a funny movie that's all I can tell you," Justin joked.

"I'm just an actor, I'm just an entertainer, I shouldn't be commenting on anything or giving anyone advice," he goes on to humbly say. "All I can tell you is that if you're gonna do that, just be safe."

When asked about both he and Mila's recent invitation to the Marine Corps Ball, which spurned other celebrity invites for Betty White and Emma Stone through YouTube, Justin seemed genuinely pleased with starting the trend.

"We opened up a whole can of worms," he laughs. "I think it's great though."

However, his presence at the ball is not for sure as he shares that he also has another movie coming out around that time.

"I'm still trying to make sure that I can clear my schedule so I can make it happen for that young lady."

Mila, who stunned in a red body-hugging Lanvin dress, also gave her two cents on the great friends with benefits debate at last night's premiere.

"I think it's possible in theory but falls short in execution," she smiles.

As for her own Marine Corps Ball invitation that she agreed to on-camera, she reveals that she hasn't yet picked out a dress for the much buzzed-about Greenville, North Carolina event.

"You know just as much as I do," she tells ET. "I don't know what I'm wearing yet. It's a couple of months away, so as soon as I know, I'll let you know."

Check out the video to see Justin and Mila work the photogs into a frenzy, and for a glimpse at a high-fashion Emma Stone in an eye-catching Giambattista Valli outfit. 'Friends With Benefits' is out in theaters this Friday.