Pretty Dog Halloween Costumes for Sale. Many of our dog Halloween costumes for sale include a comfortable dog-friendly shirt, dress, and jacket that closes with Velcro, avengers costumes as well as a headpiece with room for their ears. Your hairy darling also must be accompanying you to the party, so do some shopping for her/him as well. Apart from just Halloweens, there might be other types of costume parties as well that you are planning to celebrate, and your pooch needs to blend well and fit in the celebratory environment.