...on the set of new film "Don Jon's Addiction." So, no, they're not a couple. Although we think they'd be really cute together!

The film centers on a contemporary, porn-addicted Don Juan-type as he attempts to become less selfish. It's set for release sometime in 2013.

Scarlett, 27, has been dating New York City ad executive Nate Taylor for several months. He follows a fling she had with Sean Penn and a failed marriage to Ryan Reynolds.

We're not sure who Joseph is dating right now - if anybody. He has most recently been linked to Devon Aoki and Evan Rachel Wood.

See more photos from the set...