Whole Cake Island is the eighth island that the Straw Hat Pirates visit during the Whole Cake Island Arc. It is also the birthplace of Sanji. The island is inhabited by humans and animals, as well as an army of sentient plants called the Charlotte Family, who rule over the island and its citizens.
Luffy first arrives on Whole Cake Island in search of Sanji, who had been kidnapped by his family and forced into an arranged marriage with Charlotte Pudding. After a series of battles against the Charlotte Family and their allies, Luffy finally rescues Sanji from his wedding ceremony. However, they are then pursued by Big Mom's forces across the island.
In total, Luffy spends around two weeks on Whole Cake Island before finally leaving with Sanji and the rest of his crew.