The cleaner who stood motionless and looked directly at the camera is creator/director Stephen Merchant's father Ron Merchant.
David Brent announces that Ricky is leaving. Although Ricky didn't get a going-away present, David says "You should have seen what we got Pete Gibbons!" Peter Gibbons was lead character in the similarly-themed Office Space (1999).
Tim quotes John Lennon when he says, almost word-for-word, "life is what happens to you while you're busy making other plans". This is from the song "Beautiful Boy (Darling Boy)".
Tim mentions there a 3 nightclubs in Slough, including one called Henry the Eighth.
There was a nightclub in Burnham Beeches (Burnham is next to Slough) called Henry's for many years.