Helped a bit with an Ice King costume for Sam's friend. We took (my) white bed sheet and dyed it a proper blue. Then measured and pinned it into a poncho shaped tunic, then did a couple of (mostly) straight lines to achieve a basic tunic.
They had found a very cool mask, and I had previously picked up a length of shaggy white material for a beard. They also created a basic crown out of paper and glitzy foam. We already had some latex gloves, and voila--Ice King.
There was of course one small accessory missing--a Gunter penguin. Sam had bought some felt, and I took a crack at just doing a basic one, with the felt sewn down.
Turned out pretty cute, and so they put it underneath the beard so they could flash people with it. We put a safety pin on the back of it so he could move around though.