When looking back at the original run of Buffy the Vampire Slayer, it's hard to imagine anyone other than Alyson Hanigan playing Willow Rosenberg. She played the part of someone who made up the heart and soul of Buffy the Vampire Slayer and a character that set some new standards in this kind of series considering she stepped out of the closet as gay once the Scoobies went off to college. It's hard to imagine anyone anyone else talking Xander or Buffy off the ledge whenever they started feeling quite down. She was also the most compelling part of the show when she went dark. And her battling with the urge to go dark again was an interesting take on dealing with addiction in a world of magic.