|Real World information|
The Joker is archnemesis of Batman appearing in The Darkness\Batman comic.
The Darkness\Batman Edit
Joker is visited by Jackie Estacado in Arkham Asylum. Jackie Estacado tries to find out from Joker as to what is Batman's biggest fear. Joker in returns only says few crude jokes, which don't make sense to Jackie. Seeing that he won't get the information he wants from Joker, Jackie leaves.