Sharon Horgan admits that she struggled during the read-through of the final scene, particularly with the line "I'm sorry you find it a struggle to make me happy, because, really, you make me happy every day." She says the line made her emotional because it reminded her of her time writing with Rob.
Episode 406 deals with the death of Rob's mother, Mia, who was played by Carrie Fisher in seasons 1-3, until her untimely death on December 27, 2016. For her final performance on the show (season 3, episode 6), she received a posthumous Emmy nomination for Outstanding Guest Actress in a Comedy Series.
The ceramic model that Rob sees of a mother reading to a little boy was commissioned for the episode, not found.
Throughout the entire four-season run of "Catastrophe," Carrie Fisher was the only actor Sharon and Rob would allow to improvise during scenes.
Sharon and Rob considered themselves lucky to get the rights to use the Arcade Fire's song "The Suburbs" for the final sequence of the series. Appropriately, it's sung by a husband and wife (the band's Win Butler and Regine Chassagne), with a lyric that fits what Sharon and Rob wanted to say in the show.