11 Now make a square path by using "Rectangle Tool (m)" (don't ask "for what?", just do it, you'll see :) ).

12 Hold the mouse on "Warp Tool (Shift+r)" and choose "Crystallize Tool".

PS: any tool on Warp tool you can’t reduce the brush size, that's why you need to make the path you want to edit bigger/smaller.
Make it at least 3 shapes

13 Select the 3 paths you've made, and align them to the center by using "Align" tab next to "Pathfinder" tab.

Click on the "Horizontal Align to center" then "Vertical Align to center".

14 Reduce the size of the paths so you can fit it to the center of the eyeball. After place the paths on the center of eyeball.

Arrange the layer so the 3 paths will be on top of the eyeball and bellow the highlight, center, and blurry center of the eye.

15 Now go to "Transparency Window" and reduce the transparency.
And your work is done, and this tutorial can be used not only just for cartoon eyes but for realistic eyes too, neat eh?

Trying to be wise note: