The second episode of the first series was the show's original pilot; then the producers made some changes which is reflected in the rest of the run. Differences include the lighting and Mark Heap playing Jim as a more (quasi)masculine, less strange character.
The family was based on Robert Popper's own family.
Almost a year after the series ended Paul Ritter passed away on April 5th 2021 from a brain tumor. He was 54.
When Tamsin Greig was in discussions regarding the part of Jackie, producers told her they were looking at Paul Ritter to play Martin. Greig was a fan of Ritter's work and said she would definitely accept the role if they could get Ritter on board.
Since the end of the show, four of its actors have passed away. Paul Ritter, Frances Cuka, Rosalind Knight, and Harry Landis.