From the Super Mario Wiki
Retrieved from "https://www.mariowiki.com/index.php?title=Shadow_Bug&oldid=2278786"
Shadow Bugs are a strange kind of creatures in Super Smash Bros. Brawl. Although named bugs, they do not look much like bugs and look like round dark balls. The Halberd stores all the Shadow Bugs and releases them across the Smash World. When a lot of Shadow Bugs form together, they can create Primids and other enemies. Shadow Bugs, when they come in contact with trophies, can create another clone of the trophy. This clone is an evil side of the original character, and appear as the character with a purple tint. Shadow Bugs originate from Mr. Game & Watch, and an unlimited amount can be taken out from his body. When Tabuu learned of this, he used Mr. Game & Watch to create the Subspace Army.
Names in other languages