EXCLUSIVE: Melissa McCarthy is getting some company on the road in her starring vehicle Tammy. The New Line comedy has cast Mark Duplass (Safety Not Guaranteed, The Mindy Project) in a key role in the pic about a woman (McCarthy) who loses her job and discovers her husband is cheating, then hits the asphalt with her foul-mouthed grandmother. She meets a man (Duplass) on her trip and they develop a strange relationship. McCarthy wrote the script with husband Ben Falcone, who will direct, taking over for original helmer Beth McCarthy-Miller. Duplass just wrapped Open Road’s JFK drama Parkland and the Universal-Blumhouse horror Mercy, based on a Stephen King short story. He also stars in, produced, and co-wrote the upcoming Peachfuzz for Blumhouse, is starring in and exec producing the indie The One I Love, and is gearing up for a spring shoot on his HBO pilot with brother Jay Duplass, Togetherness. Duplass is repped by ICM.