Mechanical Genie Island is a minor location in the series, The Marvelous Misadventures of Flapjack.
There, they met the Mechanical Genie, who challenged them to a game of chance. If they were to lose, the duo would become his butlers for life. If they won, they would get freed from the island.
In the end, Flapjack and Captain K'nuckles won the game, and ended up escaping the island.