uncertaintyfilm:

The audition, like the film, was “improvised”. The actors (Joseph Gordon-Levitt and Lynn Collins) were given a dialogue-less script to read, but no lines to learn, no scene to prepare. Just the general situation that begins the film: you’re hanging out with the person you love, and you’re talking about what to do about an unexpected pregnancy.

Joe and Lynn auditioned together. Before the audition, they’d never met.