This is Halloween (song) - The Nightmare Before Christmas Wiki
" This Is Halloween " from The Nightmare Before Christmas acts as an opening, theatrical tour of Halloween Town, showcasing various monstrous residents and their dedication to scaring, ultimately introducing the Pumpkin King, Jack Skellington. The song, composed by Danny Elfman, sets the stage for the film's plot, leading into "Jack's Lament," where Jack reveals his weariness with the annual routine. This is Halloween (song) - The Nightmare Before