May 20, 2003: Superheroes were dead. Batman, thanks to George Clooney, had devolved into a nipple-clad joke, Eric Bana's "Hulk" was a month away from becoming the new standard for how not to make a comic book movie, and the first "Iron Man" film was barely a glint in Marvel's eye.

And yet there existed, and had for the seven years leading up to that day, a superhero franchise that was busy redefining what a superhero was and tilling the soil for the next generation of comic book adaptations (starting with "Batman Begins" two years later) to not only thrive, but also become the default definition of a blockbuster.

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This week we celebrate the 10th anniversary of the series finale of "Buffy the Vampire Slayer," a show that understood — better than any TV show or movie that had come before it — what superheroes are: allegories of human struggle presented as empowering fantasies. At their best, they teach children (and the inner child in all of us) how to cope with struggle and loss, to overcome obstacles, and to inspire us to be better than we thought we could be — all disguised beneath a layer of fantasy and snappy wordplay.

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Joss Whedon's vampire slayer was a superhero dressed like an ordinary girl — swap the cardigans for a cape and demons for supervillains and you're looking at an average issue of "Supergirl." The show wedded those ideas to the semiprocedural format of "The X-Files," alternating monster-of-the-week episodes with "mythology" or season-arc episodes to propel the series. It opened the door for fantasy and horror to cross over to the younger set, as seen in the success of shows like "Supernatural" and "The Vampire Diaries."

[Related: Missed the Season Finale of 'Vampire Diaries'? Catch Up With Our Recap]

On a deeper level, though, it opened new ways of exploring teen angst and, more broadly, the process of becoming an adult. Whedon allowed his characters to grow; they were able to go through the pains of being ostracized at school, the pain of first love, and the fear of leaving the familiar to make your own way in the world. It helped fuel the crossover success of "Harry Potter" and "Twilight" as adults realized that maybe what looked, on the surface, like children's stories might contain something more.

You don't have to look hard to see "Buffy's" finale as a dry run for the climax of the biggest-opening movie in history ("The Avengers," currently the third-highest-grossing film ever): a team learning to work together, ordinary people doing extraordinary things (Seriously? You're gonna fight an alien invasion with a bow and arrow?), the death of a loved one, an apocalyptic final battle, the hero's sacrifice, junk food...

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