Highly visible: Far from vanishing into obscurity, Clea Duvall, who played Marcie, has gone on to appear in films such as The Faculty, Ghosts of Mars and She's All That.

Grave matters: Although the episode is officially known as Out of Mind, Out of Sight, it is also widely referred to as Invisible Girl.

Fade away: The sequence where Marcie watches as her hand disappear in class (and, indeed, the whole episode) was inspired by a vivid dream Joss Whedon had as a child. He used to think nobody loved him and that he was invisible to those around him. How wrong he was.

Oops: Angel makes a reference to Vampires and breathing in this episode. When he saves the gang by turning off a leaky gas valve, "It's not like I need the oxygen." This ties in with Prophecy Girl, where Xander saves Buffy life because he can't administer. Yet in Surprise, we witness Angelus smoking. License is at the discretion of the show.

By the book: Angel, meeting Giles for the first time, reveals the Tiberius Manifesto and the Pergamum Codex are key accounts of Slayer lore. Although Giles believes the Codex to be lost, it turns out Angel can get his hands on a copy. He must know some great second-hand demon book dealers.