Johnny Flynn, real life composer of the series theme song, has a cameo as Johnny Piper, the performer who goes on before Andy (Mackenzie Crook) and Lance (Toby Jones) at The White Horse pub.
The characters known as Simon & Garfunkel are actually called Peters (Paul Casar) & Lee (Simon Farnaby) in the series.
Toby Jones (Lance), Mackenzie Crook (Andy) and Simon Farnaby (Art) also appeared in Christopher Robin (2018) together as Owl, Newspaper seller & Taxi driver respectively.
Gerard Horan (Terry) & Lucy Benjamin (Maggie) also worked together on episode 2.2, Episode #2.2 (2008), of Kingdom (2007) as D.C. Yelland & Patricia Wright respectively.