I love destroying people's preconceived notions about what you can do with a bike.
Although the checkers at my local grocery stores are starting to catch on, I still surprise people just about every grocery shopping trip. (Bagger who sees the helmet in my hand) "You're on a bicycle? How are you going to carry four bags of groceries?"

I stopped at the office supply place a couple weeks ago and bought a new laser printer. The box was probably 18x18x24. The cashier looked at my helmet, looked at me and raised his eyebrows but didn't say a word. I asked "are you wondering how I'm going to carry this on a bicycle?" He replied "that's none of my business".

I love my Xtracycle.