The dress shop in which Buffy admires the wedding dress is the same one in which Cordelia Chase worked in The Prom (1999).
D'Hoffryn gives Willow a talisman so that she can summon him if she changes her mind about becoming a vengeance demon. Willow will later use this talisman in Selfless (2002) in order to talk to D'Hoffryn about Anya.
Buffy mentions having met with Angel for five minutes (from her point of view) in I Will Remember You (1999).
Both Buffy and Giles are unable to see how Willow is truly feeling. Spike is able to see it right away. This perceptiveness is later exploited by Spike in The Yoko Factor (2000).
Despite the fact that it has been shown that vampires have no reflection, Spike can be seen many times in a mirror to the left of the door, visible just past Giles' shoulder and in the glass front of the bookshelf next to his chair.