King (film character)
From the Super Mario Wiki
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The King (as his role is credited) appears as a main character in the Super Mario Bros. film. He is Daisy's father and the king of Dinohattan, but had been overthrown and de-evolved by President Koopa into a giant sentient fungus that had spread across the parallel world to obstruct Koopa's construction projects.
He continually aids Mario and Luigi throughout the film in their quest to defeat Koopa. Once they successfully do so by killing Koopa, the King reverts back to his human form.
He also appears in the webcomic sequel to the film, where he is now called Reznor, his original name from the Super Mario Bros. film script. The name "Reznor" is a reference to the fights scientists believed would have taken place between the T. rex and the Triceratops in prehistoric times, due to the Reznor's similarity to this dinosaur.