Halloween

In which Buffy becomes a lady, Xander becomes a man, Willow becomes a ghost, and Giles becomes Ripper. (Exhibit D in the 'Xander is Hot' debate)

Official back-of-box synopsis:

There are lots of tricks but not many treats when Buffy's costume causes her to lose her powers and the kids she, Willow and Xander are trick-or-treating with turn into their costume characters. Could Giles have something to do with all this?

From the old WB Buffy website:

TRICK OR TREAT -- Buffy, Willow and Xander are recruited by Principal Snyder to trick-or-treat with the neighborhood kids, but the night doesn't turn out as they had planned when Buffy's costume causes her to lose her slaying ability and the other kids transform into their costume characters. Meanwhile, when Giles begins to paste together the night's events, he learns that it's his past that is making this a very haunted Halloween.

Cast:

• Sarah Michelle Gellar as Buffy
• Alyson Hannigan as Willow
• Nicholas Brendon as Xander
  

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• Anthony Stewart Head as Giles
• Charisma Carpenter as Cordelia
• David Boreanaz as Angel
• Armin Shimerman as Principal Snyder
• James Marsters as Spike
• Juliet Landau as Drusilla
• Seth Green as Oz
• Larry Bagby as Larry
• Robin Sachs as Ethan
• Abigail Gershman as Girl