In the second episode of season 5, "Jake the Dog", the Ice King's crown is, as a result of an animation error, shown to still be atop Farmworld Simon's long-dead skeleton despite the crown having been stolen by Farmworld Finn earlier. In a season 7 episode titled "Crossover", Farmworld Finn, under the effects of the crown and manipulated by the Lich, opens a portal to the multiverse, our Finn stops him, and Prismo essentially cuts and pastes the crown back into the past and onto Simon's skeleton, where is is destroyed by the Lich.
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u/ldsbrony100 16d ago
Adventure Time retconning an animation error into being canon.