Jason Segel and Emily Blunt will also star with Alison Brie in the Universal Pictures movie
Segel and Stoller wrote the screenplay, which follows an engaged couple's relationship.
Judd Apatow is producing through Apatow Productions. Stoller and Rodney Rothman also are producing. Segel is executive producing.
Erik Baiers, Universal's VP production, will oversee the project for the studio with creative executives Sara Scott.
Pratt plays Andy Dwyer in NBC's "Parks and Recreation." Ifans, now filming the role of the villain in "The Amazing Spider-Man," played Xenophilius Lovegood in "Harry Poter and the Deathly Hollows: Part 1."
Pratt is repped by CAA, managers Julie Darmody and Jimmy Miller of Mosaic and attorney Peter Nelson of Nelson Davis Wetzstein, LLP.
Ifans is repped by UTA and manager Daniel Sussman of Brillstein Entertainment Partners.