The Nightmare Before Christmas Jack Skellington Adult Costume The men's Jack Skellington costume includes the pinstriped jacket, ascot and bowtie. This Jack Skellington costume adult comes in adult sizes Medium, X-Large. This Jack Skellington costume adult is an officially licensed The Nightmare Before Christmas costume. Couples Halloween costume ideas: Jack Skellington and Sally make a great pair for Halloween! Black pants are not included with the Nightmare Before Christmas costume.