Disney's The Little Mermaid: Adult Deluxe Ariel Cosplay Costume Includes Dress & Tiara. Take Your Mer-self to the Next Level with This Sure-To-Impress Ariel Princess Costume. Make Waves with a Costume That's Fun, Flippin' Fabulous and Full of Sass! (If You Don't Find Yourself Singing Under the Sea, We'll Return Your Crustaceans!)