Mechakoopa Stomp
Bowser Crush is the fourth and final special attack Bowser learns during the events of Super Mario RPG: Legend of the Seven Stars. When used in battle, Bowser summons a giant green Mecha-Koopa that stomps across the battlefield, damaging all enemies. The player can press during the attack in order to increase damage dealt. Bowser learns this attack at level 18, and needs 16 Flower Points to use it.
The giant Mecha-Koopa used for the attack was developed by Koopa researchers for several months in a top-secret laboratory located deep within Bowser's Keep, for the purpose of stomping flowers and frightening butterflies.[1] The giant Mecha-Koopa was finished just as the Smithy Gang invaded Bowser's Keep and the Mushroom Kingdom. Bowser was initially disappointed that he couldn't use the Mecha-Koopa for its intended purpose but realized that he could use it to stomp enemies instead. Multiple Mecha-Koopas of this sort exist[2], and it is possible that a different one is summoned each time Bowser Crush is used.