From the Super Mario Wiki
Bubble Bloopers are a type of Blooper that appear in Mario & Luigi: Bowser's Inside Story. They are found only in the Pump Works in Bowser's body. They are blue, bubble shaped, and stuffed full of water.
Bubble Bloopers attack Mario and Luigi by rolling or bouncing their way; both can be countered by the hammer. Bubble Bloopers will float up to one of two levels to signal which attack they will use. If they go to the top of the bottom screen, they will roll at the brother they are targeting after landing; if they go to the top screen, they will bounce onto their target.
Mario & Luigi: Bowser's Inside Story / Mario & Luigi: Bowser's Inside Story + Bowser Jr.'s Journey
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