From the Super Mario Wiki
Super Bouncer is a Special Attack used in Mario & Luigi: Bowser's Inside Story and Mario & Luigi: Bowser's Inside Story + Bowser Jr.'s Journey. This attack, along with the Yoo Who Cannon, uses seven SP in the original game, while in the remake, it uses twelve, a two SP difference from the Yoo Who Cannon. To use it, the player must collect all 10 Energy Hold Attack Pieces.
When using this attack, Luigi hops on a giant, starred, pink-colored ball, and Mario has to spike it by pressing the button. After a while, Luigi and the ball will descend down onto the enemies. While it is landing, the player has to control Luigi to put him in the middle of the ball and press the button. After that, the ball floats down to Mario so he can spike it again. If Luigi is too close to one of the edges, if the wrong button (or no button) is pressed, or when Mario fails to spike, the attack stops.
In Mario & Luigi: Bowser's Inside Story + Bowser Jr.'s Journey, Luigi balances on the ball instead of "hugging" it, and he bounces off the enemy one last time before kicking the ball down on them at the end if the attack is performed successfully.
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