Want to dress like a biker this Halloween? Check out BikeRadar.
... Doping Cyclist: Dress up in full pro kit. Use a marker to draw needle tracks up and down one arm. Tie a length of surgical tubing above one elbow and leave a syringe sticking out of your vein. Wheel around an IV tower for the duration of the party. Stuff your jersey pockets with bottles of drugs. When anyone asks what / who you are, respond that you are a professional cyclist. When they ask what all the needles and drugs are for, say you have no idea what they're talking about. No matter what, do not admit you have any drug-related items on hand.
Other must-reads include the Roadie, the Tri-Guy, and ... yes.... the Recumbent Rider.