I went as The Dude to a party two nights ago. If you have long hair, are around 6 foot tall, and can grow a goatee it is the easiest costume ever. Bath robe, white shirt, sweatpants/shorts, sunglasses. Got a lot of compliments actually, and came up with it about an hour before the party. Luckily I hadn't shaved in a couple weeks. Now I have to walk around with a goatee till Monday though which makes me feel a little ridiculous.