The Morgul Bat's entry in the Appendices menu reads, "Those Uruks that get poisoned become horribly diseased and bloated, wearing their deformities as marks of honor. The poison slowly eats at their minds, sending them nightmares of a demonic man-bat who preys on fear."

This is a reference to Batman, most likely because of the Batman: Arkham series, also published by Warner Bros.
Contributed by Boyobmas