If so, perhaps you could go as the new ChloƩ collection? It would be a great 'concept' costume; when people inquire about the inspiration behind your homeless person getup, you could laugh condescendingly and reply, "DAHLING, I'm the ChloƩ Spring 2010 ready-to-wear collection! OBVI."
Pictured Above: Post-apocalyptic androgyny with a touch of 'crazy'