Zako Demon Beasts (魔獣) are Nightmare Enterprises' common enemy combatants. They appear in the Kirby: Right Back at Ya! anime and are similar to the regular enemies in the games.
The Zako Demon Beasts come in different types, shapes, and sizes, and are numerous in groups as well. There are different kinds of Zako Demon Beasts: Mini-Monsters, Chess Monsters, Generic Monsters, and Spirit Monsters. Noddies, Drifters, Dedede Dolls, 3 Color Fighters, Cold Viruses, Mumbies, Demon Frog, Destrayers and Air Riders can also be considered Zako Demon Beasts because of how numerous they are, as well as their appearances in large groups.
The Mini-Monsters were the first Zako Demon Beasts to be introduced in the show. They are small, miniature monsters that like to cause trouble for anywhere they go. There are ten different mini-monsters - axes, brooms, cows, cyclopses, four-armed boxers, raccoons, radishes, witch-hatted monsters, wood pieces, and wrench-armed robots. They had a small appearance in the beginning of Episode 2, "A Blockbuster Battle", and returned to have a large role in Episode 40, "Monster Management", where Knuckle Joe supplied Cappy Town with multitudes of them and let Kirby tire himself out sucking them all up before downloading Masher.
The Chess Monsters appeared in Episode 3, "Kirby's Duel Role", during a flashback Kabu did to the time when Nightmare created a monster that would not obey his orders while explaining to Tiff and Tuff about Nightmare himself. The Chess Monsters were absent for the rest of the anime series up until the final episode, "Fright to the Finish", where several Chess Monsters were seen in Nightmare's lair, except these were much larger and different in appearance than the ones in the third episode.
The Generic Monsters are probably Nightmare Enterprises' most important Zako Demon Beasts. They are notable for often being seen in flashbacks to Meta Knight's past. Their first appearance was in Episode 4, "Dark and Stormy Knight", where they, of course, were seen in Meta Knight's flashback to his past. Their first real appearance was in Episode 31, "Abusement Park", where they waited for Kirby to be uploaded to their homebase only to be easily destroyed by Mike Kirby.
There are thirteen different kinds of Generic Monsters - green gem-wearing purple lobsters, worms, mollusks, spiked armadillos, bears, silver dragons, single-horned walruses, footed seahorses, single-eyed pterodactyls, boxing glove-wearing wolves, spiked spider-like crabs, red dragons, and brown wyverns. The last appearance of the Generic Monsters was in Episode 65, "Masher 2.0", where they were helpers of Masher 2.0 while Masher was in a battle against Knuckle Joe on his home planet, and Knuckle Joe destroyed all of the Generic Monsters.
In Meta Knight's flashback in "Dark and Stormy Knight", it is revealed that the Generic Monsters have special abilities just like the ones that Kirby mainly battles. The worms can spit bolts of electricity from their mouths, the mollusks are able to cause shockwaves from their tentacles, and the armadillos are capable of breathing fire.
The Generic Monsters seem to be based on different kinds of prominent kaijuu, especially ones appearing in live-action movies and TV shows, including Godzilla, Magma from Gorath, and Gyaos from the Gamera series, as well as other kaijuu.
The Spirit Monsters were the last Zako Demon Beasts (not counting Air Riders) to be introduced in the anime. They are white, gust-like ghostly spirits with malicious faces. The monsters did not actually appear in any anime episodes, but they can be seen in the second Japanese opening, where they are released from a present to King Dedede after he and Escargoon open it, and Kirby simply defeats them by inhaling them all.