How many friends? How about Dorthy, Tin Man, and the Scarecrow!
I like the double headed dragon idea. Maybe dress in all green, and wrap alarge piece of green fabric around you and your friends bodies.
One halloween party dressed my horse up as an angel, and I dressed as the devil. You could be two devils, and make her an angel. Or even dress her up as something, and you be an angel, friend is the devil. You can make a blonde wig, get a feather boa, and use fabric to make a dress for the horse. I dunno
~*~Never approach a bull from the front, a horse from the rear or a fool from any direction. - Cowboy saying~*~