It's nice to see just how popular Hilbert curves are. For me it touches the same nerve that Conway's Game of Life does.
I threw together a hacky demo of the Hilbert curve and some other l-system curve for a middle school computer club I ran way back when. Not the best UI in the world, but it shows you either the string substitutions following each l-system ruleset, or with "show canvas" checked each click draws the next generation.