paper airplanes. What would be even more cool is to make paper airplanes from notes, so you take a piece of paper, write something on it, and THEN make it into an airplane that can be thrown. +1 if it can be thrown into an adjacent (random if multiple) street.
Naturally, items folded from notes can be unfolded. :)
Oh, I LOVE this! Especially the idea of lanterns with fireflies in! I have firefly jars around my house, but I always feel like they're suffocating.. :(