Although credited, Alexis Denisof doesn't appear in this episode. This was due to his wedding to Alyson Hannigan at the time of filming. This is the only episode after he made his first appearance in Parting Gifts (1999) in which he does not appear.
Fred refers to Gunn as "Gunn" in this episode as opposed to "Charles" as we see in previous episodes. Perhaps this is intentional, emphasizing the fact that the couple have now parted ways.
This episode reveals the first time that Spike and Angelus actually meet, in 1880.
Adam Ward, the first assistant/focus puller, says the scenes at the abandoned Opera House were unexpectedly difficult to film. "It's one thing to see it on camera and another being on location in this theater that hasn't been used other than for film shots for decades. You get in there and the matter that floats around looks great on camera but you just don't want to breathe it in."
In a flashback to 1880, Angelus says, "William. You know, you really should find a new name for yourself. It just doesn't strike the right note of terror." This provocation might be the reason why William found the reasons to re-name himself Spike.