Sesame Street Martians: "Yip, yip, yip, yip." That's what you'll be saying all night if you're going to be one of the martians on Sesame Street. What you need to do: Get styrofoam for the eyeballs and pipe cleaners for the antennae. You will also need lots of material to drape over yourself. You'll need to make sure the mouth area is a black mesh material, so you'll be able to see from the inside of the costume. More instructions here. Source: Reddit user zb2good via Imgur
Yip-Yips from "Sesame Street," so when she found some Muppet-like fabric at JoAnn Fabrics, she couldn't resist making these costumes for her kids. The Yip-Yips' eyeballs are made from Styrofoam and the antennae from pipe cleaners. Inside the costumes are foam hats that make the heads a bit pointy and the lips are foam-filled and attached to a stick, so the wearer can move the mouths with ease.