Jitterbug is a yellow insect who appeared on the Sesame Street episode Good-bye, Elmo, Hello, Jelmo. He started the jitterbug dance in the Fix-it-shop before the orange-gold member refused to repair the destroyed juicer.
The puppet used for the Jitterbug was recycled from Bug on The Adventures of Elmo in Grouchland. His third appearance was on Panwapa and he was renamed as Bill the Bug.
For a full gallery of Bug and it's characters that's been on other shows, See Jitter Bug/Gallery.