I used the basic Owl Hat Beanie pattern for the beanie and then added the minion style eyeball.

The square beanie is inspired by the shape of this sack beanie pattern;
http://www.ravelry.com/patterns/library/graphed-beanie---...
I made it in yellow with the black stripe and added the minion eye.

This is a basic eye pattern;
https://www.youtube.com/watch?v=crWUgOHXYvo
I make the first round black for the pupil, use a variegated yarn for one round for the iris and then 2 rounds of white.