"[Buffy is] a feminist challenge to gender hierarchy," the actress behind the Chosen One writes on Instagram.

Like all diehard Buffy the Vampire Slayer fans, Sarah Michelle Gellar is sharing her own memories and gratitude for Joss Whedon's genre-busting series.

The series, which starred Gellar as TV's most beloved vampire slayer, debuted 20 years ago today and helped change the way women were portrayed on the small screen and left a lasting impact on not just viewers but the actress as well.

Gellar reflected on the show's rough road to the screen as well as its legacy in a lengthy Instagram post in which she called the former WB network series "the little show that could" and Buffy a "feminist challenge to gender hierarchy." Read her full post, below. Click here for THR's deep dive with Whedon; here for our chat with exec who opened the door fora Buffy TV series; and here for some of the cast on the show's legacy.

Here are some of the other great ways in which the Buffy stars celebrated the show's 20th anniversary: