After Ted's night with Sassy, she says that she's going to order a huge breakfast and charge it to his room. He replies "I'll be your Underhills anytime." This is a reference to the film "Fletch" in which the character is always charging things to a married couple named "The Underhills". Sudeikis was once considered to play the role of Fletch in a reboot of the series.
Ted says "all this Chandler Bing-ing aside ..." after using sarcasm and wild gestures to help Roy get to the root of his relationship issue with Keeley, referencing the "Friends" character which was famous for both.
Based on the scores needed to finish the game of darts, Rupert and Ted were playing a game of 501 using double in/double out rules.
The darts scene in 1.8 was originally planned as a cricket game.
At 26 minutes Mae rings the pub bell. Bell ringing is usually reserved to announce last orders before a pub closes for the day.