WILHELM SCREAM: about 15 minutes in, when Connor throws a knife into someone's wrist.
When Sunny brings Connor to the abandoned motel, they enter a room that has "GIO" spray-painted on the wall, a reference to the character Gio from That Old Gang of Mine (2001).
Joss Whedon explains his decision to instantly bring Connor to adulthood: "What are you going to do? Have a baby running around? I don't think so...That's the beauty of it being a fantasy show."
The character Sunny may be a reference to a character by the same name in The Catcher in the Rye. Both girls are poor teenagers who are encountered by adolescent men in times of need (Connor and Holden Caulfield respectively). Both men are dealing with separate existential crises. While Sunny from the novel is a prostitute, Sunny from the episode is a drug-addict.
In his cataloging of vampire-slaying methods, Connor forgets holy water.