Oops! Forgot to post this in March.
The pattern is Invader Zim GIR Knit Hat by Yarngear (Mei Lynne Travis).
I think I've had the pattern in my Ravelry queue for years. I don't remember adding it so when I stumbled on it when updating my queue last week, I had to make it for my sister.
It has a knit in hem which is really awesome. You basically knit your brim 2x as long as you want it to be, fold it, and knit the stitch and the corresponding cast on loop together.
I used Red Heart Super Savers and US#8/5mm needles for everything since I don't really have needles in other sizes. I also crocheted the eyes instead of knitting them.