Pet Costumes - Halloween Costumes & Costume Supplies for Dogs: Don't leave your beloved pooch out of the Halloween fun and festivities. Popular costume manufacturers are coming out with more and more costumes for your pet!!! And, they will melt your heart! From Halloween costumes to Christmas costumes, don't miss all of our popular pet costume themes below. Check the sizing closely; These costumes are not just for toy breeds and Chihuahuas!