Jawbreaker — 1999
There's no doubt that this movie was inspired by the '80s cult classic Heathers and absolutely set the scene for Mean Girls. Rose McGowan stars as the ultimate queen bee and leader of the "Flawless Four." Also in the clique are Rebecca Gayheart, Julie Benz, and Charlotte Ayanna (though Ayanna isn't in the film for long, since they accidentally kill her by jamming a jawbreaker in her mouth). In order to cover up their crime, they recruit school outcast and witness to the murder Fern Mayo (Judy Greer) to join the clique.