A good friend gave the kid an Elmer Book and a stuffed Elmer doll, which has become one of her favorites to gnaw on.
Elmer is different from other elephants; he's covered with patchworks in all the colors of the rainbow. Sometimes, he gets sad when he feels different from the other elephants. But then he learns that it's best to have confidence in who he is, and that it's good to respect people's individual talents and differences. Things are more colorful that way.
There's a whole series of Elmer Books (I count 8 on Amazon); apparently he has quite a few adventures. I'm confident that, when the time comes, reading and discussing Elmer's Friends will make it much easier to explain Ernie & Bert to the kid.