4. Bert and Ernie, 'Sesame Street'
These two characters taught generations of children what friendship was. Such was the singular genius of Muppets creator Jim Henson that the personalities of Sesame Street's BFFs could be determined through phrenology alone: Round-headed Ernie was exuberant and humorous, while pointy-noggined Bert was buttoned-up and serious. Henson's TV creations did not suffer from a shortage of memorable duos — Kermit and Piggy, Statler and Waldorf, Big Bird and Mister Snuffleupagus — but the orange and yellow roommates at the center of his long-running show were his yin and yang par excellence.