I wanted a cookie monster costume for halloween, so I looked up how to make furry costumes (a strange rabbit hole), deadmau5 heads, and emailed a friend for advice. Here's what came out of it -

The head is based on a construction helmet. You can see a cable coming down to my hand. That's a repurposed brake lever from a bike. Squeezing the lever makes the mouth move.

I covered the head in blue fur, and I made my friends and parents put the head on. The eyes are foam 4" craft balls, and they're held in by bolts. The lower jaw is a plastic ruler bolted on to the helmet. The eyes are buttons. I wanted the manic googly eye effect cookie monster is known for, but it didn't work well with the foam and buttons. I'll have to try again using another method.

The body suit is a copy of a Tyvek painting suit from Home Depot. I ripped out all of the seams, stole the zipper, and copied it exactly on this blue fur. You can copy the Tyvek pieces directly onto the fur, because the suit is so huge. There's no need to leave seam allowances. The whole suit required about 5 yards of fur. Its warm and weighs a lot. This was my first time sewing a zipper, and it went pretty well.

My girlfriend was a cookie, so we took this picture together. The whole thing looks better with the head tucked in, but it was such a hot night that even short periods in full costume were unbearable.