Laboon is a colossal whale from the West Blue—easily as massive as the monsters lurking in the Calm Belt. The Straw Hats meet him right after entering the Grand Line, where he's been waiting at Reverse Mountain's base for the past fifty years. A long time ago, a pirate crew befriended him and left him there, but never came back. Since whales are social creatures that travel in pods, Laboon formed an incredibly strong bond with them and has basically been stuck in limbo ever since, refusing to accept they're gone.
The whale's caretaker is Crocus, an old doctor who runs the Lighthouse at Reverse Mountain. He's been looking after Laboon all these decades. It turns out the pirates who abandoned him were Brook's crew—making Laboon one of the few people the skeleton still has a real connection to. Though Laboon knows the truth about what happened to them, he won't accept it. You can see it in the scars all over his head from repeatedly ramming into Reverse Mountain, convinced he can smash through and sail back home.
Luffy, recognizing a kindred spirit, decides Laboon needs hope again. He challenges the whale to a fight, deliberately ramming the Going Merry's mast into his head. After calling it a draw, Luffy makes a promise: he'll come back for a rematch. To seal the deal, he paints the Straw Hat Jolly Roger on Laboon's forehead with a caveat—the mark will fade if Laboon keeps slamming the mountain. It's Luffy's way of giving the whale something to believe in while they sail off into the Grand Line.
Content compiled by AnimeList.moe from publicly available sources.
