Creative Horse Costume Ideas?

Okay, so I have exactly one week until my big horse show, and I have been training so hard, I completely forgot about the costume class! I need some ideas for a horse/rider costume that are creative (e.g. not like Indian pony, pirate, etc.). I have a 16'3 hand Tennessee Walker, who doesn't appreciate loud and scary things, like balloons. I can show in this class either mounted or in hand, it doesn't really matter. Any cheap, easy, fast, or creative ideas are greatly appreciated!