Indigo

 Dr. Indigo (Dr. インディゴ) is an ingenious member of Shiki's crew. He is the one that created Boss and the other monstrous animals under Shiki's dominion.

Appearance
Indigo is a huge man with a mime-like appearance. He has indigo hair, with two particularly large tuffs at the side of the head, and his face is white, with purple lines near his eyes, presumably some sort of make-up. He is pot bellied, with thin limbs, and a muscular torso. On his forehead he has a pair of purple round-shaped eyeglasses. He wears a large yellow polka dotted indigo scarf and indigo-striped shoes (similar to Kuro's) that make a farting noise every time he takes a step. He also wears indigo overalls, with two lines of bottons on the front, and a lab coat over them. On his hands there is a pair of brown gloves.

Personality
Indigo is a doctor with an eccentric personality: he has a distinct laugh which goes "Piro piro piro", adorns shoes that emit sounds of flatulence whenever walking, doesn't caring if others gets irritated by this, and also often tries to act like a mime, but usually breaks character by suddenly talking. He also appears to be prudent, as he always carries around a phial of antidote to the Draft disease, just for precaution.

Shiki
Indigo shares a rather humorous relationship with his captain Shiki. Whenever Shiki says or does something stupid, Indigo acts as a straight man and slaps him, after which they both present themselves to others like a typical comedy duo after a joke. Regardless, he is loyal to Shiki and spent twenty years creating super-powered creatures in Merveille for the Golden Lion Pirates to take over the world. He also plays a part in Shiki's dances, along with Scarlet

Abilities and Powers
Indigo is a chemist of sorts. He was the one in charge in the development of Shiki's scheme involving all the monstrous animals. He may be a strong fighter who uses scientific materials since he was seen along Shiki and his crew when they fought against Gol D. Roger and his crew. He's possibly a skilled swordsman, as he was seen attacking Luffy with a sword fitting his size, and wielding it during the battle in Shiki's palace.

Indigo is also a skilled dancer, taking part in all of his captain's little "dance shows".

Chemical Juggling
He has the ability to produce explosive chemicals from his body and attack with them, called Chemical Juggling. He uses his ability to create chemical orbs, that are then arranged above him and shot from his hands, causing explosions. He can also create a larger orb with a far more explosive effect, which he calls Mass Juggling. The way he manipulates the chemicals resembles to the skill of Juggling. It is unknown if this ability stems from a Devil Fruit or from some sort of chemical he used on himself.

Trivia

 * Of Shiki's main crew members, they all have a color in their name.
 * The reason his scarf is always hovering behind him (as if wind was blowing through it) is because there is a wire inside the scarf.
 * Indigo shares many distinctive traits with the character Mayuri Kurotsuchi from the series Bleach: they're both scientists with eccentric personalities, blue hair, seemingly painted faces and using particular abilities related to chemicals. Also, in the original Japanese version, they have the same voice actor.