The Manta Ray first appears spying on Nemo, Flip, Princess Camille, and Professor Genius entering Nightmare Land and flies off to alert the bat-like goblins about Nemo and the King Morpheus's scepter.
The Ray appears again discovering Nemo, Icarus, and the Boomps riding Nemo’s bed towards the Nightmare Castle and informs its master. When the Nightmare King discovers his goblin minions failed to capture Nemo and the scepter, he angrily absorbs every monster in his castle, except the Ray.
During the final battle, the Nightmare King orders the Ray to kill Nemo and capture the scepter. Nemo manages to defeat the ray by using the scepter’s power to create a blade, and slices off one of the Ray’s fin-like wings. The rendered flightless Ray met its end by crashing into a wall and explodes.
The Ray appears in both the 1990 Nintendo NES video game Little Nemo: Dream Master and the 1990 Capcom arcade game Nemo. In the NES game, it is the boss of the 2nd level in the final world of the game, and appears in the Arcade game as a recurring enemy in the last level of the game, before the final showdown with the Nightmare King. In both games, the Ray can only be defeated by using the power of the scepter.
- The Manta Ray's real name and gender is unknown, as it was never mentioned in the film.
- The Manta Ray only has a minute of screen-time, and does not appear in the film until the last half hour.
- The Manta Ray's position in the Nightmare King's army is unknown, but it can be presumed it is his pet, as it was the only creature not absorbed by the King during his breakdown.
- In Little Nemo: Dream Master, the Manta Ray attacked Nemo by spewing fireballs, which it never did in the film nor the arcade game.