From the Super Mario Wiki
Broggy Bonker is a Special Attack used by Bowser in Mario & Luigi: Bowser's Inside Story and Mario & Luigi: Bowser's Inside Story + Bowser Jr.'s Journey. This attack costs 20 SP to use in the original, and 28 (30 on Easy) to use in the remake, the highest amount both games for Bowser. It is one of the strongest Special Attack in the game, the other being Falling Star, which is used by Mario and Luigi. Bowser can use this move after finding all 15 Blitties found inside enemies throughout the game using the Vacuum Block and giving them to Broque Monsieur at his shop in Dimble Wood.
When initiated, Bowser will be carrying a filthy Broggy. After throwing Broggy off-screen to start the move, Bowser will get out a broom and start to scrub the dirt off of him. The player will have to clean Broggy as much as possible by rubbing him with the stylus. The cleaner Broggy is, the more damage the enemy will take. When executed perfectly, Broggy will ram into the enemy, multiple if the attack yields a "Great!" rating or less, or going up into the air and slamming down on them if the attack yields an "Excellent!" rating. After the latter outcome happens, Broggy will then come from behind the enemy and rush into them, with a line of Blitties following him to deal extra damage.
In Mario & Luigi: Bowser's Inside Story + Bowser Jr.'s Journey, Bowser will toss a bar of soap on Broggy before he starts to clean Broggy with the broom.
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