I was hammering up a hill one afternoon, and a couple was walking down on the side walk, not far away. ( No parked cars at the time, for some reason. ) The guy looked over at me standing on the pedals, holding the bars, and pushing myself up the grade, and said "I could do that." His girlfriend laughed in a way that made it clear she didn't think he'd ever be able to bike up a steep hill. That was fun, for me...