My roomies in college had to do this experiment. One was very extroverted, and she went to the grocery store dressed a little crazy (lots of layers, a funny hat, sweats tucked into socks, gloves in the late spring, etc) and she talked to a few few people in the store very politely, and was very chatty but kind with the cashier. We were in a small town, and the reactions to this were fabulous - a lot of raised eybrows and comments. But even though she LOOKED crazy, people were visibly surprised when she was actually very nice and normal in behavior.
My other roomie was a little less extroverted. She was on a weekend trip, and asked several people if she could borrow their toothbrush because she had left hers at home. Talking to individual people that you know and asking a question that invades personal space might be the way to go. She got wonderful reactions, and people thought it was hilarious when she explained to them that she had to do it for class.