Paul Klee meets Perry the Platypus

I was playing around with something in Mathematica and one of the images that came out of it surprised me.

It's a contour plot for the system function of a low pass filter.

 H[z_] := 0.05634*(1 + 1/z)*(1 - 1.0166/z + 1/z^2) / ((1 - 0.683/z)*(1 - 1.4461/z + 0.7957/z^2)) ContourPlot[ Arg[H[Exp[I (x + I y)]]], {x, -1, 1}, {y, -1, 1}, ColorFunction -> "StarryNightColors"]

It looks sorta like a cross between Paul Klee's painting Senecio

and Perry the Platypus from Phineas and Ferb.