From the Super Mario Wiki
“You got it! I'm ornery as all get out! Prepare for some pain!”
After Mario defeats General Guy and his Shy Guys in Shy Guy's Toy Box during the events at the end of Chapter 4, Mario comes back to Toad Town as usual and decides to go to the docks to get to Lavalava Island to get the fifth Star Spirit, Misstar. When Mario sees a Whale having a belly-ache, the Whale begs Mario to check its stomach. After that, the Whale opens up its mouth and Mario makes his way into its belly. Inside, Mario sends Watt out to light up the darkness, and Fuzzipede is revealed hanging from the ceiling. Fuzzipede starts to jump around the Whale's belly, but Mario fights him and forces him out of the Whale.
After Mario defeats Fuzzipede, he explains that he got eaten by the whale while trying to get away from Fishmael. By then, the Whale says that he is actually feeling good now that Fuzzipede is off his stomach wall. Then water starts to fill up the Whale's Belly, popping Mario, his partners and Fuzzipede out through his blow-hole. Fuzzipede forgives the whale after getting out of the belly as he goes away.
He's a Fuzzipede. What a weird little creature! People use Fuzzipedes as fish bait, but they often manage to cut the line. He's pretty robust for such a little guy.
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