Adjust variables with arrow keys/mouse, then press space. Pensize: The Pen size. Affects the quality of the drawing. Turns: How many times the sensor turns to sense how far it is from the cat. FadeDistance: How far the sprite has to be from the cat before it only draws completely black dots.
Inspired by something I'm doing in art class. EDIT (9/5/16): Changed how the pixels are drawn. They're now drawn in squares instead of circles, and they're drawn after the distances are calculated.