Sneak Peak of 'Batman: The Killing Joke' Offers a Teaser and a Featurette That Delves into the Joker's Dark Past

This Killing Joke covers what's widely accepted as the origin of the Joker and some of the events that lead up to Barbara Gordon (Batgirl) becoming paralyzed (after which she eventually becomes Oracle). There's also a featurette with more explanation on the origin of the story and the people working on this movie: