In Yu-Gi-Oh! Duelist Duel 51: "Toons Attack!", Yugi Mutou speculates that since this card isn't circulated to the general public, it seems to be an original card made just for Pegasus, being the only one in the world.
According to Pegasus, the page the "Toon World" book is open to is called "Evil Castle", and is the lair of "Toon Summoned Skull".
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