Opening DeKnight: Blood Ties was the first script from newcomer Steven S. DeKnight. He'd only popped in to the Buffy offices to discuss the Buffy animated series with Joss Whedon, but soon found himself signed up to become a regular staff writer. He will be writing scripts for the animated series too.

Eh, Oh!: Cute BBC bundles of pre-school fun the Teletubbies get a name check in the episode. The show is widely syndicated in America.

Two become one: So Ben is Glory and Glory is Ben. Wow.

Clare Kramer told the BBC Buffy site about the special effects involved during a recent interview. "The morphing (into Ben) was a big technical process, especially the first couple of times we did it because nobody really knew what we were doing.

"For example, the first time we morphed you see Charlie [Weber, who plays Ben] talking to the Key. All of a sudden it�s me morphing. That was about a five hour process.

"He would be standing there in a certain position and then they�d be like "Okay, freeze." He�d run out and I�d run in and stand on an apple box so I could be the same height. I'd adjust myself and they�d be yelling at me from the monitor, "Move a little to your left" or "a little to your right."

We�d finally get in the right position and then you�d come out of the morph. It�s quite an extensive process in terms of filming."

Candles: The kind of candles the relight themselves once they re blown out used to scare both Willow and Tara. There's also a unicorn-shaped one in the Magic Box. A reference to Harmony, perhaps?

Memories: Puzzled as to why Dawn can't seem to remember Ben turning into Glory? Don't worry, it's not a gaffe, it all gets explained (in a very funny way) later in the season.

Previously on Buffy's Birthday: Other great birthday epsodes for the Buffster include Surprise (where she turns Angel into Angelus), Helpless (where she's robbed of all her Slayer strength and is forced to fight the bloke from the Bacardi ads) and Doomed (where she has to thwart another Apocalypse).

Oops!: When Dawn stares at the swing in the playground, she has a flashback - remembering her and Buffy playing there years before. Surely, even with everyone's warped memories, neither Dawn or Buffy would have been in Sunnydale at that point? Maybe it's a different swing?

Music: Holiday by Star Ghost Dog plays during Buffy's birthday party.