By day, mild-mannered Stu (Kumail Nanjiani) works a soul-crushing job at a sporting goods store, for an obnoxious younger boss, Richie (Jimmy Tatro)—the son of the store’s owner. Richie has given Stu the nickname of “Stuber” because Stu also works as an Uber driver to pick up extra cash. Stu has always been a bit …