The Pack

In which the gang go on a field trip, observe the mating habits of zebras, the swarming habits of bullies, and Xander gets in touch with his inner predator. (exhibit A in the 'Xander is Hot' debate)

Official back-of-box synopsis:

Buffy and Willow discover that all men are animals when Xander and the other boys from school are possessed by bloodthirsty demonic hyenas.

From the old WB Buffy website:

WELCOME TO THE JUNGLE - When Buffy and the rest of Sunnydale High endure the annual field trip to the zoo, Xander and some other kids sneak into the quarantined hyena exhibit, but leave in an altered state. It's up to Buffy, Giles and Willow to discover the cause behind Xander's bizarre behavior and reverse the transformation before it's too late. Meanwhile, Xander's new aggressive demeanor doesn't play well with his old friends.

Links:

This episode's page at http://www.restlessbtvs.com/, the Restless BTVS Trivia Guide

This episode's page at http://www.vrya.net/bdb/, the Buffyverse Dialog Database

Cross-reference:

episodes in which humans die in conflict with Buffy:

• What's My Line? (part 1)
  the assassin at the ice-rink
• Go Fish
  Coach Marin and Nurse Greenleigh
• Homecoming
  Hans and Frederick Gruenshtahler
• Revelations
  Gwendolyn Post
• Spiral
  Some of the Knights: they're human, right?
• this episode
  the Zookeeper

Cast:

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

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• Anthony Stewart Head as Giles
• Ken Lerner as Principal Flutie
• Jeffrey Steven Smith as Adam
• Eion Bailey as Kyle
• Michael McRaine as Rhonda
• Brian Gross as Tor
• Jennifer Sky as Heidi
• Jeff Maynard as Lance
• James Stephens as Zookeeper
• Gregory White as Coach Herrold
• David Brisbin as Mr Anderson
• Barbara Whinnery as Mrs Anderson
• Justin Ross as Joey
• Patrese Borem as Young Woman