The Shroobs are a race of aliens from the Shroob Planet that invaded in the Mushroom Kingdom when Mario and Luigiwere babies, as shown in the game Mario & Luigi: Partners in Time. They are a purple, mushroom-like species ruled by Princess Shroob and her older sister. Unlike the similar, yet much more benevolent Toads, who are seemingly more humanthan mushroom, Shroobs seem to have retained most of their fungus ancestry.

They possess very advanced technology, such as ray guns and a massive fleet of flying saucers, powered by the vim of Toads, which is collected by capturing the Toads and draining the vim through the Shroobs' Tree Network, all leading to the Vim Factory. The saucers are capable of shooting energy bolts that turn people into Shroob Mushrooms, as well as causing devastating damage to buildings. The Shroob military is very complex in their processes. They come in different colors and have different attacks. Unlike the Koopa Troop, the Shroobs have everything laid out in advance so that they could both protect vital operations and invade enemy regions at the same time, suggesting they are very intelligent.