Willow Danielle Rosenberg is a fictional character created for the fantasy television series Buffy the Vampire Slayer (1997-2003). She was developed by Joss Whedon and portrayed throughout the TV series by Alyson Hannigan. Willow plays an integral role within the inner circle of friends--called the Scooby Gang--who support Buffy Summers, a teenager gifted with superhuman powers to defeat vampires, demons, and other evil in the fictional town of Sunnydale. The series begins as Buffy, Willow, and their friend Xander are in 10th grade and Willow is a shy, nerdy girl with little confidence.

The seventh season starts with Willow in England, unnerved by her power, studying with a coven near Giles' home to harness it. She fears returning to Sunnydale and what she is capable of doing if she loses control again, a fear that dogs her the whole season.  Buffy and the Scoobies face the First Evil, bent on ending the Slayer line and destroying the world. Potential Slayers from around the globe congregate at Buffy's home and she trains them to battle the First Evil. Willow continues to face her grief over Tara's death and, reluctantly, becomes involved with one of the Potentials, Kennedy (Iyari Limon).  In the final episode of the series, "Chosen", Buffy calls upon Willow to perform the most powerful spell she has ever attempted. With Kennedy nearby, cautioned to kill her if she becomes out of control, Willow infuses every Potential Slayer in the world with the same powers Buffy and Faith have. The spell momentarily turns her hair white and makes her glow--Kennedy calls her "a goddess"--and it ensures that Buffy and the Potentials defeat the First Evil. Willow is able to escape with Buffy, Xander, Giles, and Kennedy as Sunnydale is destroyed.  Through the gamut of changes Willow endures in the series, Buffy studies scholar Ian Shuttleworth states that Alyson Hannigan's performances are the reason for Willow's popularity: "Hannigan can play on audience heartstrings like a concert harpist... As an actress she is a perfect interpreter in particular of the bare emotional directness which is the specialty of [series writer Marti] Noxon on form."

What happens when she casts the spell?
attempted. With Kennedy nearby, cautioned to kill her if she becomes out of control, Willow infuses every Potential Slayer in the world with the same powers Buffy and Faith have.