Shroob Rex

A Shroob Rex is an enemy species in the Mario series, first and as of yet only appearing in Mario & Luigi: Partners in Time for the Nintendo DS. They're a Shroob variation of the Rex species that originated in Super Mario World. They can be found only in Shroob Castle, a location in the game that actually takes place in Princess Peach's Castle, albeit a building taken over by the Shroobs. They don't serve much importance other than guarding the castle.