From the Super Mario Wiki
“Boss... Nothing happen yet, brah...”
Hornfels is the boomer in Flint Cragley Cragtrotter. He is partners with Monzo and is one of Flint Cragley's crew. He appears in the Floro Caverns of Super Paper Mario and goes wherever Flint tells him to go.
During the game, Hornfels got lost in the Floro Caverns (as did Monzo) and Mario, Princess Peach, Bowser and the Pixls had to find him and tell him where Flint Cragley was. After that, Flint blamed Hornfels (and then Monzo) for not having and losing the key that let them go deeper in the Floro Caverns. As it turned out, Flint had the key in his pockets (which might be a reference to Beldam blaming Vivian for losing Mario's sketch and the Superbombomb in Paper Mario: The Thousand-Year Door). After that, Hornfels still followed Flint everywhere.
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