Oompa belongs to the Boomps, peculiar animal creatures inhabiting Slumberland's wilds. The group includes Oompa, Oompo, Oomp, Oompy, and Oompe. They possess unique immunity to the Nightmare King's dark powers. Encountering Nemo and his companions in goblin-infested Nightmare Land after Flip's map becomes unusable, the Boomps offer aid in rescuing King Morpheus. The Boomps exhibit shapeshifting abilities, though the specifics remain undefined. They provide crucial guidance through Nightmare Land following the map's damage. Their presence becomes vital after the Nightmare King's minions capture Nemo's initial companions, leaving Nemo and Icarus dependent on the Boomps for support. After Nemo awakens in his room following a failed attempt with the royal scepter, the Boomps, including Oompa, appear alongside Icarus, demonstrating their ability to traverse between Slumberland and the waking world. During this encounter, their lost member Oompo arrives bearing a message from the imprisoned King Morpheus containing the scepter's full incantation. The Boomps then lead Nemo and Icarus through a portal in the sky towards the Nightmare King's castle. Throughout the final confrontation, the Boomps assist Nemo in navigating the castle's obstacles and contribute to battling the Nightmare King's forces. Their collective efforts aid Nemo's victory, resulting in the Nightmare King's defeat and the purification of Nightmare Land. The Boomps' loyalty and aid prove instrumental in overcoming the threat to Slumberland.