For one of my final projects in the metals class I took in college I constructed a working, movable tricycle. It rolls, steers, and pedals. It's tiny and I love it.
We were asked to create a piece that had a story behind it. When I was young my grandfather told me a joke that had a tricycle as part of the punch line. Every time I drive by the place that he told me the joke I remember him. It's lovely.