As Buffy is leaving the social services office, she can be heard whistling "Going through the Motions," the opening song from Once More, with Feeling (2001),
When Buffy shows up at the Magic Box invisible, Xander asks her if she's been feeling ignored and Buffy responds that this isn't a "Marcie" thing. This is a reference to season one's Out of Mind, Out of Sight (1997) where a student, Marcie, became invisible inadvertently when everyone ignored her.
While Buffy was invisible she stopped a kid from bullying a girl and this line was cut: "Watch who you bully, kid. She might be the next chosen one."
Sarah Michelle Gellar had requested to cut her hair, so the writers made her haircut a plot point of this episode and she wore a wig for the first few scenes of the episode.
Buffy first recognizes that she does in fact want to live - something that she has been struggling with since her return in Bargaining: Part 2 (2001). This also marks the changing, rehabilitation part of Willow and Buffy's separate problems - Willow's addiction to magic, and Buffy's disdain for being alive.