in reply to Hilbert Curve
Of course (hence 'featured', not 'introduced'). I'm guessing XKCD was not around in 1891. That's why I linked Wikipedia first. More info at the following excellent sites: Hilbert Curve at Mathworld and Peano Curve (more general) at PlanetMath.
Update: Oops. Just looked at your profile, which states that you hate xkcd and wikipedia. Sorry for the salt in the wound.