Mr. Freeze was planned to appear in the game, but was removed because the character has no personal grudge against Batman or Joker, as such he would not fit within the story. Freeze's cell can still be found in the Asylum's penintentary, however.

The Mad Hatter was also planned to appear in a garden maze controlled by Poison Ivy. This was removed when developers found it didn't match the game's tone. However, the Mad Hatter's riddle was still placed in the garden area.

Both characters would later appear in Batman: Arkham City.