Name's the Same: Russell T. Davies likes reusing names. Tyler is one of his favourites — here it is Vince's surname, and later it was to be Rose's surname in Doctor Who. There are also characters named Martha Jones and Donna, both of which were used as names of major characters in Doctor Who.
Prop Recycling: Stuart buys Vince a replica of K-9 in an attempt to buy his affection, and it plays a prominent MacGuffin role in the last couple of episodes. The replica is the BBC's actual K-9 prop.
California Doubling: Set in Pittsburgh, Pennsylvania, filmed in Toronto. Which makes the show hard to watch for some who know Pittsburgh well.
Irony as She Is Cast: Michael says in one episode, "I thought straight actors don't accept gay roles?" Hal Sparks is straight, as are Gale Harold (Brian) and Scott Lowell (Ted).
Screwed by the Lawyers: The streaming versions had much of the music replaced with banal soundalikes, causing significant damage to the story and atmosphere. Among the most frustrating examples is an early episode where the cast are out dancing and, in the original, react with delight to the iconic opening of ABBA's "Dancing Queen"; in the streaming version they inexplicably react with delight to ... something completely unremarkable and unrecognizable.
Unintentional Period Piece: The fashion isn't usually too of the moment, but the solid-tie-identical-to-the-shirt combo Brian wears at the office in one season 1 episode dates it absolutely to the year of production (late 2000).