Joss Whedon characters in How I Met Your Mother

Top to bottom; left to right:

• Danny Strong (Trey)
  Jonathan Levinson - Buffy the Vampire Slayer

• Alyson Hannigan (Lily Aldrin)
  Willow - Buffy the Vampire Slayer

• Neil Patrick Harris (Barney Stinson)
  Dr. Horrible - Dr. Horrible’s Sing-Along Blog

• Cobie Smulders (Robin Scherbatsky)
  Agent Maria Hill - The Avengers

• Alexis Denisof (Sandy Rivers)
  Wesley Wyndam-Price - Buffy the Vampire Slayer/Angel

• Amy Acker (‘Rain Dance’ Penelope)
  Illyria - Angel and Dr. Claire Saunders - Dollhouse

• Morena Baccarin (‘Crazy-Eyes’ Chloe)
  Inara Serra - Firefly/Serenity

• Tom Lenk (Scott the ‘Swarley’ barista)
  Andrew Wells - Buffy the Vampire Slayer

• Harry Groener (Clint)
  Mayor Richard Wilkins - Buffy the Vampire Slayer