From the Super Mario Wiki
Not to be confused with Mouser
Meowser is the name used for the Cat form of Bowser introduced in Super Mario 3D World. Bowser obtains the form once, in the final battle sequence of World Bowser-Castle: The Great Tower of Bowser Land. He has white and orange fur with brown stripes, similar to a tiger's, a ringed tail, cat ears instead of horns, whiskers, and his nose is black. Also, his hair is colored red, white, and brown, and his shell appears to become more gray-blue, looking similar to Dry Bowser's. Like Cat Goombas and Cat Bullet Bills, the form is more akin to a transformation than a suit. The name is a portmanteau of "Bowser" and "meow", the onomatopoeia for the sound that a cat makes.
The form makes its only appearance in the final section of The Great Tower of Bowser Land, as he uses the form in an attempt to fight Mario and his friends. Like Cat Mario, Meowser can climb walls and swipe his claws at his enemies. Unlike Cat Mario, however, his tail is large enough to whip, like Tanooki Mario, as well as retaining his ability to breathe fire (though he uses this less often). After Mario attacks him with a POW Block, Meowser uses the power of Double Cherries to become Double Meowser, spawning up to five doubles to fight Mario. The player cannot harm Meowser directly; the only way to finish the fight is to hit the Giant POW Block 5 times at the top of the tower to defeat Meowser. The Clear Pipe to the Goal Pole will then be revealed.
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