- "In my day, no self-respecting creature of the night went out on All Hallow's Eve. We left that to the posers, the blighters who had to dress up and try to be scary."
Halloween or Hallowe'en was a holiday celebrated annually on the night of the 31st of October. Originally a pagan holiday, in modern times it had come to be associated with the supernatural. However, demons and vampires traditionally avoided hunting or attacking on Halloween and "took the night off" because they believed it to be an idiotic cliché. However, Wolfram & Hart traditionally celebrated Halloween with an annual Halloween bash organized by the firm's Entertainment Division.
On Halloween night 1997, sorcerer and chaos worshiper Ethan Rayne caused havoc by enchanting those who bought costumes from his costume shop to magically transform into whatever they were dressed as. 
On Halloween 2001, Buffy and her friends celebrated with a party, whilst Dawn Summers went out with her friend Janice Penshaw and two young vampires: Zack and Justin. Zach and Justin belonged to a gang of "rebels" who decided to break the rules and go hunting.
On Halloween 2003, Wolfram & Hart, now under the management of the Angel Investigations team, organized their annual Halloween bash, but strange events occurred because Lorne, the new head of the Entertainment Division, had his ability to sleep removed to cope with the demands of his new job; lacking the ability to sleep while still possessing the need to do so, Lorne's subconscious eventually physically manifested as a means of coping with the subconscious conflicts that Lorne would normally have processed as he slept. It went around, attacking and seemingly killing all those who had recently angered Lorne, though it vanished when Lorne's ability to sleep was returned.
18th Century Girl
Little Red Riding Hood
Hot Rocker Chick Ghost
Joan of Arc
Bunny (her biggest fear)