Dragon Curves
One of the most versatile space filling curves is Heighway's Dragon.

The dragon curve can be created by folding a strip of paper
over and over, then opening each fold to ninety degrees.
Using turtle graphics higher order dragons can be made by replacing each
line with two shorter lines ninety degrees to each other, alternating the
direction.
Continuing this to its limit makes the standard dragon.
Simply by changing the angles between the segments, a family of mutant
dragons can be created.
Some mutations retain there space filling properties.
All of these are just small changes in the shape of the dragon, there are
many other interesting things you can do with dragons.
All of these images were created using turtle graphics in
PowerLogo.
The
Spanky Fractal Database
contains several
Fractint L-systems files,
including some interesting dragons.
The file
TEACHOUT.L
contains some dragons similar to the ones on this page.