It will be First Come, First Serve. Superman Costume for dog Superman dog costume is of polyester fabric that will not cause any discomfort to your darling pooch. Also keep in mind that open registration for the contest at the convention will take place Friday and Saturday. If slots are full on Friday, check back in on Saturday to see if any drop-outs have occurred. Yes, Fotnite costumes are rocking the Halloween and any such costume parties everywhere these days.