... because it was never localized to English in official sources.
Imohmushii (lit. Worm or Green Caterpillar) is a minor character that appears only once in the entire anime for a very short portion of episode 23, The Empty Nest Mess. It is a caterpillar that Escargoon found in King Dedede's Castle garden and uses it as a demonstration for his Insta-Monster-Mixture formula that he had created. The caterpillar was injected with Escargoon's serum and eventually grew and transformed into a huge monster mutant that squashed King Dedede and Escargoon. After its short-lived rampage, Imohmushii picks up Escargoon with his mandibles and swings him about virtuously. It was at this exact moment when Dedede happily realized that the invention worked and that he could make all the monsters he wanted without having to spend money buying them from Nightmare Enterprises. Imohmushii never appears again after this scene, so whatever happened to him after his small appearance in the beginning of the episode is unknown.
Imohmushii starts out as a small, fuzzy purple caterpillar Escargoon finds wandering around on the castle grounds. While still in this harmless form, its body consists of three dull purple sections with small orange spots on them. It has a small, light green head, olive green legs, and an orange mouth. Shortly after being injected with Escargoon's formula, it grows into a giant monster and gains solid silver mandibles, glaring blue eyes, and bright golden spikes running down his back in the process, now having nine purple segments.
Imohmushii is the first monster in the anime that Kirby never fights.