Dan Aykroyd and Allison Janney have joined the cast of Tammy, which will mark the directorial debut of star Melissa McCarthy.

The story follows the title character (Melissa McCarthy), who loses her job at a fast food restaurant and discovers her husband is cheating on her at the same time. She decides to take a road trip with her profane, whiskey-swilling grandmother (Susan Sarandon). Dan Aykroyd will play the father of Mark Duplass' character, who encounters Tammy and her grandmother on their road trip. Allison Janney is playing Tammy's mother.

Melissa McCarthy is directing with her husband Ben Falcone, from a script they both wrote together. Production is scheduled to begin next month.

Dan Aykroyd most recently starred in The Campaign, and lends his voice to the upcoming animated film Dorothy of OZ. Allison Janney will next be seen in Touchy Feely and The Way, Way Back.