The Yoko Factor

In which the Scoobies discover the enemy - and it's them. Oh, and Adam and Spike.

Official back-of-box synopsis:

Showdown for Buffy's heart - Buffy is even more certain of her love for Riley when Angel's surprise visit to Sunnydale brings Riley and Angel to blows.

From the old WB Buffy website:

DAVID BOREANAZ GUEST-STARS IN A SHOWDOWN FOR BUFFY'S HEART - Buffy is even more certain of her love for Riley when Angel's surprise visit to Sunnydale brings Riley and Angel to blows. Meanwhile, Spike joins forces with Adam and devises a plan to tear the Slayer apart from her gang, leaving her wide open for her enemies to attack. David Grossman directed the episode written by Douglas Petrie.

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 Giles sings:

• Where The Wild Things Are
  "Behind Blue Eyes"
• Restless
  "The Exposition Song"
• Once More, With Feeling
  well, duh
• this episode
  "Freebird"

episodes in which our heroes get drunk:

• The Dark Age
  Giles - whisky
• Beer Bad
  A Very Special Buffy
• Something Blue
  Willow's "Not drowning, wading" in light beer
• A New Man
  Giles -- again -- too many beers with Ethan
• Life Serial
  Buffy - Tequila - priceless look on her face
• Entropy
  Spike and Anya. Hilarity ensues. Oh, wait, not hilarity.
• this episode
  Giles - whisky - again

episodes which cross over with Angel episodes:

• The Harsh Light Of Day
  Oz goes to L.A. for "In The Dark"
• Pangs
  Angel visits Sunnydale; Buffy then visits him in "I Will Remember You"
• Dirty Girls
  Faith comes to Sunnydale, having been fetched in "Orpheus" by Willow
• this episode
  Angel in Sunnydale, following Buffy's visit in "Sanctuary"

episodes with major moments in Willow and Tara's relationship:

• Hush
  Willow and Tara meet
• Who Are You?
  "I am, you know" - Willow and Tara get together for the first time
• The Body
  their first public kiss
• Once More, With Feeling
  Tara realises Willow's using magic to influence her
• Seeing Red
  losing Tara, Willow will never be the same again
• this episode
  Willow says for the first time that Tara's her girlfriend - "bloody hell!"

Cast:

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

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• Anthony Stewart Head as Giles
• David Boreanaz as Angel
• James Marsters as Spike
• Marc Blucas as Riley
• Leonard Roberts as Forrest
• Amber Benson as Tara
• George Hertzberg as Adam
• Conor O'Farrell as Colonel McNamara
• Bob Fimiani as Mr Ward
• Jade Carter as Lieutenant