Actress Alyson Hannigan portrayed Willow Rosenberg for all seven seasons of Buffy the Vampire Slayer, but she wasn't the only person cast in the role. Riff Regan was originally cast as Buffy Summers' best friend for the TV series created by Joss Whedon. Regan only completed the unaired Buffy pilot before the role was recast, leading to Hannigan getting her chance at a breakout role.

Willow attended Sunnydale High with her closest friends, Buffy and Xander. She was a bit of a nerd with a shy personality, which made her a target of bullies at times. Despite the ridicule, Willow retained her upbeat demeanor. Upon learning of Buffy's identity as a Slayer, she helped found the Scooby Gang, often acting as her friend's sidekick. As the series went on, Willow emerged as a powerful witch. In addition, she grew more confident in her own skin and eventually came out as a lesbian.

Related: Buffy the Vampire Slayer: What Happened to Buffy After the Series Ended

Before the official Buffy premiere, "Welcome to the Hellmouth," debuted in March 1997, an unaired Buffy pilot was created in 1996. The twenty-five-and-a-half-minute pilot followed a similar plot to the broadcast counterpart, but there were a few major differences, including Regan's portrayal as Willow. The pilot was used to pitch the series to networks, but Whedon had been outspoken about not being a fan of the finished product. Those who have seen the low-quality production will instantly notice that Regan didn't seem like a fit for the series. She didn't have chemistry with the rest of the cast, and the character came off as timid. The version of the character never grabbed the attention of the audience in the way Hannigan's Willow managed to, so it was no surprise that the role was recast.

Hannigan Put A Different Spin On Willow Rosenberg

Alyson Hannigan as Willow and Sarah Michelle Gelllar as Buffy in Buffy the Vampire Slayer

Aside from the role of Principal Flutie, the role of Willow was the only part that required a recast after the series was picked up by The WB. Before Buffy came to fruition, Hannigan had a few years of acting under her belt. She appeared in the film My Stepmother Is an Alien, as well as the shows Free Spirt, Roseanne, Almost Home, and Touched by an Angel. When Hannigan auditioned for Willow, she gave the teenager a sense of innocence and an upbeat attitude. She defined the character differently than Regan, giving Willow a sense of pride, making her eager to help her friends, not burdened by it.

It's no question that Whedon made the right choice in hiring Hannigan to play Willow. The character appeared in all 144 episodes, making her and Buffy the only two characters to do so. Hannigan also gained a loyal fanbase, especially for her part in representing the LGBT community on network TV. The actress reprised her role as Willow for three episodes of Angel, and has voiced the character in several spinoff projects. Regan, on the other hand, retired from acting a few years after exiting from Buffy the Vampire Slayer. She has since found opportunities working for a non-profit and working at a start-up in Boston.

Next: Every Buffy The Vampire Slayer Actor In How I Met Your Mother