When Mark and Jez are at Mary's flat and she's beginning to show signs of a mental breakdown, Mary tells Mark, "My bone's got a little machine." This line is taken from the song "Bone Machine" by the alternative rock band the Pixies, which opens their 1988 album "Surfer Rosa."
The Mitre Tavern, which is used as the setting for the pub that Merry hands over to Jeremy and Super Hans, has been closed since 1999.
It is revealed that in college, Mark had a brief sexual encounter with a woman who he called "Carol Banana Face". She is mentioned again in the deleted scenes of Quantocking. (S3E6)
Sophie is seen reading the book, "A Child Called It".
In a running gag on poorly conceived business names (esp. band names), Super Hans suggests naming the bar "Free the Paedos," - but upon Jeremy's reaction they passively settle on "The Swan and Paedo."