The movie "Nightmare Before Christmas" is classified as a Halloween movie due to its dark and gothic themes. While the story is set during the Christmas season, it is not a typical Christmas movie in the sense that it has a lot of dark and scary elements. The movie is about Jack Skellington, the Pumpkin King of Halloween Town, who accidentally discovers Christmas Town and becomes obsessed with it. He tries to bring the spirit of Christmas to Halloween Town, but things don't go as planned. The movie is considered a Halloween classic and is often played during the Halloween season.