Joker murdered that reality's version of Jason Todd. As a result, Batman suffered a breakdown and became more violent and aggressive. Brandishing a handgun, he tracked down the Joker and avenged Jason Todd's death by shooting him to death.
- Mental Illness: Like most versions of the Joker, the Earth-51 Joker was hopelessly insane.
- This version of the Joker is germane to the original iteration of Earth-51 prior to its destruction by Monarch and Superboy-Prime.
- Another version of the Joker later came to Earth-51 as part of Monarch's Army and was killed by the New Earth Jason Todd, now under the guise of Red Robin. This version of the Joker was not native to the Earth-51 reality.
- 3 Appearances of Joker (Earth-51)
- 2 Images featuring Joker (Earth-51)
- Quotations by or about Joker (Earth-51)
- Character Gallery: Joker (Earth-51)