Nyasu, a Meowth and one of the three members of Team Rocket, appears as a recurring supporting character in the film Pokémon: Giratina & The Sky Warrior. He is a small feline Pokémon distinguished by the fact that he can speak human language, a rare ability for his species. In this story, Nyasu travels with his partners Musashi and Kojirō with their customary aim of capturing rare and valuable Pokémon, and the group quickly becomes interested in the mysterious Shaymin that Ash and his friends are escorting. When the trio attempts to snatch Shaymin, they are pulled through a portal into the Reverse World, the strange parallel dimension where the legendary Pokémon Giratina lives. Once inside, they discover that they cannot find a way back to the normal world and are left stranded there. Faced with this predicament, they begin assisting Newton, a scientist who studies the Reverse World, effectively becoming his helpers while they look for a way out.

In terms of personality, Nyasu is cunning, boastful, and driven by self-interest, often coming across as the most scheming member of the trio while still being prone to complaining when situations turn dangerous. He frequently bickers with his partners, but he remains loyal to them and works alongside them even in difficult circumstances. His motivations in the film are consistent with those of Team Rocket: he wants to capture Shaymin in order to earn recognition and reward from his organization. Once the group is trapped in the Reverse World, however, his priorities shift toward survival and escaping the dimension, and his usual ambitions take a back seat to the greater chaos caused by the villain Zero and by Giratina's conflict with the other legendary Pokémon. He relates to the main characters as an opponent and rival, though the usual rivalry becomes secondary to the larger threat facing both worlds.

Nyasu does not undergo any major personal transformation during the film, but the situation forces him and his partners into cooperation with people they would normally oppose, including Newton and the heroes. His notable abilities include his command of human speech, which allows the trio to communicate, negotiate, and improvise plans in ways ordinary Pokémon cannot, as well as his physical moves typical of a Meowth, such as Fury Swipes. In the movie his practical contributions are limited and largely comedic, but he remains a recognizable presence among the group caught between the schemes of the human antagonist and the clash between legendary Pokémon.