Brook is first introduced as a skeleton inhabiting the region of the Grand Line known as the Florian Triangle. He is a former member of the Rumba Pirates, a crew of musicians who sailed the Grand Line from West Blue over fifty years prior to the current time frame of the story. They were followed by the whale Laboon, who took a particular liking to Brook's peculiar afro and his enchanting music. Promising to return after sailing the Grand Line, the crew left Laboon at the lighthouse at Reverse Mountain, stating that the Grand Line is too dangerous for such a small whale. After entering the Florian Triangle, Brook's entire crew was slaughtered by an unknown pirate crew. Because he ate the Yomi Yomi no Mi, a Devil Fruit that allows the user to come back to life after dying, Brook's spirit returned to the Grand Line, however, he got lost due to the intense fog in the Florian Triangle. After wandering for some time, he finally found his body, which had decayed to nothing but bleached bones leaving only his afro (which remained due to strong roots). Brook was returned to life as a walking, talking skeleton. During the time he spent alone on his former crew's ship, he had almost no contact with other human beings, possibly leading to his eccentric behavior such as his perverted nature or over the top sense of humor (he has a constant urge to make bone jokes).
Eight years before meeting the Straw Hat crew, he was captured by Gecko Moria, who stole his shadow and placed it in the body of the legendary samurai Ryuma. Because he could no longer be exposed to sunlight, a side effect of having no shadow in One Piece, Brook remains in the Florian Triangle, under the protective cover of the thick fog, until he meets the Straw Hat Pirates.
His goal is to circle the Grand Line and return to Reverse Mountain, reuniting with the whale, Laboon, and fulfilling the promise the Rumba Pirates made. He carries a recording of the crew, whose last survivors played their cheery song "Bink's Sake" with their dying breaths. He fears Laboon will not recognize him (being all bones now) without his afro, so he does all he can to protect it. It seems Zoro and Brook share respect for one another, likely because they are both swordsman, and in the battle with the flying fish riders in, they do a team attack showing their abilities as two skilled swordsmen.
According to Eiichiro Oda, Brook most resembles a horse. He is identified by the colors black and white, and he smells of tea.
Brook is currently the oldest Strawhat, being more than 50 years in difference to the second oldest, Franky. He is also the tallest Strawhat, excluding Chopper's Monster Point form.
Though Brook did not appear in the story until 2007, Oda planned to include a skeleton musician in One Piece ever since drawing the Laboon arc in 2000.
Brook is known for his strange personality, being a combination of a gentlemanly persona and a perverted sort. He speaks in a dignified, educated manner at most times, but is known to have amazingly bad manners (burping and farting at dinner, casually asking to see womens' panties, picking at other peoples' food, etc).
Brook is also known to adore bone puns. He takes any chance he can to make a comment about his skeletal nature, almost inevitably following with "Yoho! Skull joke!!" Example: "I was so shocked, my eyes nearly popped out of my head! BUT I HAVE NO EYES!!"
Brook has a distinct laugh, always known to give off a jolly "Yohoho!"
Powers and abilities
Brook carries a shikomizue (Japanese cane sword), and is extremely skilled in its use. He can also combine his shikomizue and violin to create sound-based attacks. He was once a fighter in the surprise-attack squadron of an unknown kingdom. In addition to his sword skill, Brook's lightweight skeleton body gives him great speed and the ability to jump extraordinarily high. His body is so light that he is even capable of running on water, however, Brook is still powerless if submerged in water, like all Devil Fruit users. Brook is also an excellent musician, displaying the ability to play any instrument at a highly skilled level. He's even capable of playing songs that drive anyone who hears them to sleep, which proves to be useful in combat. Brook claims he can heal from most fractures to his body by drinking milk. His head can also be opened up and used as a storage device, which is currently being used to store a Tone Dial containing the last song of the Rumba Pirates. Brook uses an unnamed fencing sword style and is actually quite a skilled fencer and can use quick stabs because of his skeleton anatomy.
One of his signature attacks is the "Arrow Notch Strike", a sword technique so fast that the actual strike is not seen, and the recipient is unaware they have been struck until a significant amount of time after the attack (usually a few seconds, about the amount of time it takes to resheath his sword).
During his time on Thriller Bark, Brook developed a reputation among the inhabitants as a mysterious warrior who would sing a haunting tune just before he struck down a squad of zombies in a flash. This turned out to be because Brook himself was afraid of the horrible place, and sought to calm himself by humming or singing as he went. He also used his superior speed to mow down the opponents, mostly so that he could not scare himself with their appearance.
While dead and seemingly able to last long periods without food or water, Brook's body seems to be able to act as a normal person's. That is, he is either shown or implied to be able to eat, drink, cry and digest normally. His skeletal body may possibly give him enhanced resistance to pain or injury, as he would be more difficult to injure without blood or organs.