The Yip Yips
The Yip Yips are alien visitors from Mars who appear on Sesame Street. They are silly and love to learn about Earth. They have big eyes, tentacles, and antennae. They speak by making yip-yip noises and they often say "nope nope nope" when they don't understand something. When they're scared, they cover their face with their lower jaw and make a goom noise.