With a few variations a form-fitting, stretch fabric, one piece outfit can be the the basis of many styles and genres of costume. At it's most basic it's a human form with an abstract texture. With a few additions it's the center of many anime/ cosplay and comic book recreation costumes. It's suppleness, flexibility and slightly fleshy texture can combine with fabric paint and a few other materials to portray all sorts of wondrous creatures.

  It also serves the purpose of an undersuit. A unitard base can complement and save wear and tear on many costumes. For heavier costumes an undersuit can keep the costume cleaner, wick off sweat and prevent itches or chafing. Anyone with a varied costume collection could use an all purpose black utility skinsuit.

  You could build a more complicated costume around a stretch fabric base. A costume based on a skinsuit could have excellent fit and mobility despite it's bulk. Gluing and sewing padding and stuffing to the skinsuit to simulate mass and muscles can make a highly realistic creature costume with an understructure that shifts naturally below it's skin. If the under suit is removable maintainence, cleaning and wear of the costume can be made far easier.