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Brown Rocks are obstacles in Mario & Luigi: Superstar Saga. They are found throughout the Beanbean Kingdom, serving as roadblocks for Mario and Luigi. They can be destroyed by any type of hammer, including Super Hammers and Ultra Hammers. They are first introduced at Hoohoo Mountain, in the home of the Hammerhead Bros., who forge a hammer out of a Hoohoo Block for Mario and Luigi. Brown Rocks are mainly used early on, serving as a tutorial for using hammers in the field.
In Mario & Luigi: Superstar Saga + Bowser's Minions, they appear as heavily-cracked grey rocks.