The Beanbean Brooch is an item in Mario & Luigi: Superstar Saga. It looks like a blue and green gem with yellow spheres around its edge.
Lady Lima gives this item to Mario after he and Luigi defeat Queen Bean. The Queen was force-fed a Belly Blech Worm by Cackletta, thus turning her into a muscular, yet less intelligent version of herself. The only cure is the Chuckola Reserve, located in Chucklehuck Woods. The Beanbean Brooch is used as to pass the guards in front of Château de Chucklehuck, which sits on the edge of Chucklehuck Woods.