Two Suckers on a Stick
What you need: a stick, a candy shop owner, a customer, 2 unsuspecting volunteers
What you do: Pick two people from the audience and have them hold the stick and tell them its the candy counter. have the candy store owner stand on one side and the customer stand on the other.
Customer: Do you have any Jelly Beans?
Customer: Do you have any licorice?
Customer: Do you have any Snicker Bars?
Customer: Well what do you have?
Owner: I got two suckers on a stick.
NOTE: You can add as many types of candy as you want and make sure the volunteers can take a joke.