Justin & Mila Run for Fun on Set

These two always seem to be having so much fun on set! Mila Kunis and Justin Timberlake made a run for it on the set of their new flick, Friends With Benefits in L.A. on Tuesday. We don't think we've ever seen them with anything but a smile on while shooting scenes in NYC, and it seems that grinworthy way to work is going to carry over to the West Coast!

OK! GALLERY: JUSTIN TIMBERLAKE PULLS UP TO SET WITH MILA KUNIS

Mila and Justin both have new movies coming out, so it's a good thing they're finishing up production on this one so they can promote their upcoming releases.

OK! GALLERY: NATALIE PORTMAN STRIKES THE PERFECT POST WITH HER BLACK SWAN CO-STARS

Mila stars in creepy ballet thriller Black Swan alongside Natalie Portman — who is also in Friends With Benefits — and Justin will appear next in the movie based on Facebook, The Social Network.