FREUDIAN SLIP: wear a slip that has Freudian terminology written all over it: ie Oedipus Complex, Penis Envy, Seduction Theory, Libido, Id, Ego, Superego. You can also wear wire rimmed glasses, a white moustache and goatee, and carry a cigar.
COAT OF ARMS: cut the sleeves off of old shirts and then attach gloves to the ends of the shirt sleeves with safety pins. After that, attach the sleeves (arms) with gloves to a coat and wear it.
OLD ST. DICK: dress as Santa Claus and have a VERY protuding private part, which is also clothed in Santa Claus garb. Harness it in the same way reindeer are harnessed, then play the part, walking around shouting 'WWhhhhooo Boy' as you pull back on the reigns.
CEREAL KILLER: Option 1: dress in cereal boxes and stick pieces of cereal all over you and carry a fake bloody knife. Option 2: dress in cereal boxes and stic cereal all over you, carry a large spoon, and say funny things implying that you killed various cereal characters (ie Captain Crunch, Lucky the Leprechaun, Trix rabbit, Toucan Sam, etc). For added effect, carry a white stuffed rabbit (ie Trix) that looks beat up or dead.
DICKTATOR: dress in all black close fitting/leotard type clothes with a potato tied around your waist, hanging in front of your groin. (Dick-tater, get it?)
BRICK-LAY-HER: the woman dresses as a brick and the man dresses in overalls with a trowel.
PHANTOM OF THE OPRAH: dress as Oprah Winfrey and add a white Phantom of the Opera mask.
MIGHTY MORPHIN POWER LUNCHER: wear a Mighty Morphin Power Ranger costume, sans mask, and carry some chi-chi restaurant menus.
EVIL SEAMEN: wear all white outfits - t-shirts and pants - with white sailor caps, wrap around sun glasses, and x and y (chromosomes) written all over your shirts.