The project had originally been planned as a starring vehicle for Philip Seymour Hoffman, but was put on hold after the actor's death until the role could be recast, with Steve Coogan now in the lead role.
The ad agency of McMann Goldsmith and Tate shares a similar name as the advertising agency on Bewitched (1964): McMahon and Tate.
Showrunner, Shalom Auslander, was originally a memoirist. Happyish is his first script. Katheryn Hahn's reaction to this was "I just thought this is great, he doesn't know what rules there were to break."