In the grim future of The Dark Knight Returns, Batman is old, and dying, and as such his skill as Batman isn't as good as it once was. Enter Carrie Kelley, a young girl who helps Batman beat up some muggers. Seeing her passion and potential, he takes her in as a Robin temporarily. But then once she saves his life after the battle wtih the Mutant Leader, he fully accepts her as a Robin.
Carrie Kelley is a huge part of the Dark Knight books, including the current one that's being released right now. She's never afraid to do what needs to be done to help Batman, including distracting Superman with the Batmobile, or even dressing up like Batman to trick people.
Her role in the original books were so well liked that DC Comics introduced a version of her in the New 52, which is set on the "prime" earth. Where she is a friend and schoolmate of Damian Wayne.