Nightmare Princess first appears in the episode "Orb." While she is called a princess, she does not appear to have a specified kingdom, being seen only wandering the ocean surrounding Ooo.
Nightmare Princess appears throughout the episode, "Orb" as simply a cloud with a single eye. Once she is fully constructed, this cloud is shown to be her head. She wears a red dress with a yellow crown-like pattern on the abdomen. Her limbs are green with her right hand being a mantis claw and two bat wings protrude from either side of her head.