Bowser Jr.'s Boomday Machine

Bowser Jr's Boomsday Machine is a massive robot-like tower with firebar, a plasma cannon, and fans that can blow away and destroy the clouds that Mario creates with the Cloud Flower. During the third phase (after you hit the cockpit of the machine twice), the bottom of the machine comes out of the ground and becomes mobile, thanks to its tank tracks. This also makes it taller and harder to climb to the top of

To deal damage to the Boomsdsy Machine, you must climb to the top of the machine, using cloud-flower clouds and fans, and ground-pound the cockpit, which is glass

To defeat this boss, you must ground-pound the cockpit three times. Once this is done, the tower will blow up and the Grand Star will emerge, allowing you to progress to World 6