Actor Nick Offerman is joining the cast of Amazon and BBC’s supernatural drama Good Omens. In the six-part series, which is based on the novel by Neil Gaiman and Terry Pratchett, Offerman will play a U.S. Ambassador and father of a child who is mistakenly believed to be the Antichrist. The former 'Parks and Recreation' star is the latest high-profile actor to join the series, which will feature Michael Sheen as the angel Aziraphale and David Tennant as the demon Crowley.