It's hard to believe it's been 20 years since "Clueless" first hit theaters. And by "hard to believe," we mean "we refuse to acknowledge how old we're getting."

Since the movie's debut, we've learned a lot about it, but not everything -- like how crazy the casting process was, or that they had a special surprise guest during that party scene in the Valley.

Here are 20 things you might not have known about the ultimate teen movie.

[Source: IMDB, "As If!: The Oral History of Clueless as Told by Amy Heckerling and the Cast"]