The scene in South America is in reference to Lovers Walk (1998). When Spike is drunkenly confiding in Willow, he mentions he caught Drusilla making out with a Chaos Demon. The Chaos Demon, matching Spike's description as "slime and antlers," is in the middle of the argument between Spike and Dru.
It is revealed how Spike got the scar over his left eye, which James Marsters actually got when he was mugged in New York.
The poem snatched from William's hands is the first draft of the poem that Spike later reads in its complete form at the open-mike event in Not Fade Away (2004), this time received with enthusiastic applause from the audience.
This episode marks the final appearance of Darla on this series.
It was revealed Spike's character real name is "William Pratt", and also originally a famous actor's name but in most movies fans know him as Boris Karloff.