Books
Golden Super Mario Bros. "Look Look Book"
Page 11
After a long search, Iggy and Spike finally rounded up the Mario brothers and brought them to Koopa. When questioned, Mario told him that the crystal had been stolen, but Koopa didn't believe him.
"Give me that crystal or I'll turn you into slime!" Koopa warned.
Koopa had created a de-evolution machine that could change anyone into their most primitive form—slime. It had turned King Bowser, Daisy's father, into the fungus that now covered the city. The machine could also make people very intelligent, but Koopa didn't tell Mario that.
