From the Super Mario Wiki
King Clawdaddy attacks by walking around and rotating his claws when Yoshi is nearby, much like a normal Clawdaddy; the attack can be avoided using the giant Donut Blocks in the room. He will also spit out bubbles in Yoshi's direction; the bubbles themselves are harmless, but some of them contain Shy Guys that can damage Yoshi. To damage him, Yoshi must remove the foam on his body by licking it or throwing eggs; once the foam is completely gone, Yoshi can hit King Clawdaddy with an egg to damage him.
Once hit, King Clawdaddy will become angry and turn red, charging in Yoshi's direction and spinning his claw before replacing the foam and returning to normal. He will charge three times after the second hit, and produces more bubbles and Shy Guys with each hit. Once hit three times, King Clawdaddy is defeated, and World 4 is unlocked.
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