Brook

Brook is the musician of the Straw Hat Pirates. He is a skeleton the Straw Hats found on board a ghost ship after drifting into the Florian Triangle. He is a Devil Fruit user who ate the Yomi Yomi no Mi and is an undead being brought back into a pseudo-immortal state because of its powers. He is the ninth member of the Straw Hat crew and the eighth to join Luffy's crew. He is also one of the two swordsmen onboard their current ship with the other being Zoro. He fills the role of the long awaited musician that Luffy wanted for his crew since his journey began.

Appearance
Brook is an extremely tall skeleton dressed in formal attire complete with top hat and cane. At 8' 8.5" in height, he is the tallest member of the Straw Hat crew. Despite having no skin, he still has an afro which he says is because his hair has very deep roots. Brook's style is that of a gentleman consisting of a coat, top hat, pants, and afro which are black while the inner linings of his coat are yellow-orange. The ribbon tied in between his coat and around his neck is blue. The outer covering of Brook's cane sword which he carries is purple. Also, due to his many years of seclusion his clothes have become somewhat tattered.

After two years, however, he has changed to more colorful and high-end clothes, as though to represent a rock star. He has heart-shaped sunglasses, a yellow feather boa, a top hat with a giant crown on the brim and orange pants with a pink floral design.

Before his death, Brook was a tall, skinny man with a rather distinctive face. He had a slight goatee on his chin and some side burns. He typically wore shades. On his forehead was a scar that slightly resembles a diagonal omega sign (Ω). This scar was retained in his skeleton state as a distinctive crack across his skull. Brook's facial appearance, accompanied with his style of clothing, resembles a type of appearance that is commonly associated with various music artists such as Ozzy Osbourne, Slash, and other musical celebrities with similar features.

According to Oda Eiichiro, the colours that represent Brook are black and white, he resembles a horse and he smells of tea.

source: onepiece.wikia.com

Franky

Franky (フランキー) is the shipwright for the Straw Hat Pirates. He is a 36 year old cyborg from Water 7 and was introduced in the story as the leader of the Franky Family, a group of ship dismantlers. He was originally named Cutty Flam until he threw away his original name for his nickname per the request by Iceburg to hide his identity. Franky and his followers were originally introduced as antagonists of the Water 7 Arc against the Straw Hats until circumstances forced them to become allies. Per the request of the Franky Family, Franky was allowed to join the Straw Hats to fulfill his dream. He is the eighth member of the Straw Hat crew and the seventh to join Luffy's crew. He is also the second member to have been a former antagonist (the first being Nico Robin).

Appearance
As a direct result of his modifications that he's conducted upon himself as well as years having spent as a ship dismantler, bounty hunter, and street thug in Water 7, Franky is a powerfully built man with a height of at least seven feet, and he is the second tallest member of the Straw Hats. His forearms are relatively enormous while his biceps are comparably small. He has brightly-colored blue hair and blue star tattoos on his forearms. His choice of clothing usually comprises of a speedo, which causes people to call him a pervert, and an open loud Hawaiian shirt that has a large golden chain necklace around his neck. During the Straw Hats separation, after blowing up Vegapunk's laboratory, the skin gets burned off Franky's face. He also has a pair of sunglasses which he usually wears when things start to get serious.

According to Eiichirō Oda, Franky most resembles a bull, he is represented by the color light blue (cyan), and he smells of cola.

After the two year time-skip, Franky is first seen to have a hair in the style of a buzz cut, and later on, he reveals that his hair is now controllable and can change different styles instantly by pushing down on his nose for more than three seconds. He also has two stitch-mark scars on his torso running down from his the back of his neck indicating that he had sewn his skin back on, making it seem more than likely that he has finally fashioned his metal 'endoskeleton' to wrap around his entire body, and not just his visible front (since the initial operation to become BF-36 was done by himself, he could not do work on his own backside). His shoulders, torso, and arms are also much bigger than before, and with studded hands that look almost robotic in appearance, but he also revealed that inside of his huge arms he still has his real normal-sized hands. He now appears to be wearing metal rigged suspenders. He has replaced his elbows with large, light blue hinges, his shoulders with a large red ball and socket joint with 'BF-37' labeled on them, and his forearms with large, light blue cubes, with his trademark star retattooed being split by an edge. These new features house upgrades he gave himself during the last two years, but their true potential and ability has yet to be fully shown.

source: onepiece.wikia.com