Joker (ジョーカー, Jōkā) is a first-string member and the surrogate leader of the Noah's Ark Circus, tasked with managing the shows and performing as the pierrot. At Baron Kelvin's manor, Joker acts as Kelvin's butler.
Joker is a twenty-five-year-old man with purple eyes and long orange hair with extensions, which are bleached at the tips and braided at the strands. He frequently wears light-blue make-up, which he uses to paint a tear drop under his left eye, and has multiple piercings in each ear, four on the left and three on the right, wearing thick silver hoop earrings.
Joker's outfit is comprised of a yellow bow, a purple coat trimmed with gold draped off his shoulders and used like a cape, a black and lavender checkered vest with a white ruffled button up shirt worn underneath, puffy short pants with diamonds on the seam, and black and white boots that reach to the knees and curl at the toes. He also dons a white glove on his left hand. Additionally, his right arm is missing, and replaced by a skeleton arm prosthetic.
Joker is a kind, easy-going, and cheerful individual, who strives for the mirth of others, as shown when he intentionally drops balls he was juggling on his head for the amusement of the audience. Despite this outer appearance, though, he is very serious about his duties and does not easily give in to emotions.
Joker displays great care for the other members of the circus, but puts pleasing Baron Kelvin, no matter how abhorrent he finds his requests to be, above them. His motive for complying with Kelvin is that he believes he is protecting his brothers and sisters back at the Renbourn Workhouse by doing so.
Joker was born on April 2, 1863, without a right arm. He had a mother, a prostitute named Karen Taylor, but she abandoned him for an unknown reason. Joker met the other first-string circus members in an East End alley, which he calls "a gutter where every dirty being emptied its bowels" and where "everyone in this gutter was thrown away." They had no hope of getting work, and were not even skilled thieves.
Ten years ago, Doll rushed up to Joker one day with a tooth in her hand. She gleefully exclaimed that it fell out, believing that she would later get a coin from the Tooth Fairy and promised them that she would buy them all bread afterwards. Peter began to retort that the Tooth Fairy didn't actually exist but was prevented from doing so by Jumbo. When he angrily questioned why he didn't allow him to speak, Joker agreed with Jumbo that it was hard to break the truth to her whilst seeing her smile, additionally musing that gap teeth are too cute to be legal. Beast commented that if Doll did not get her coin next morning, she would be extremely upset, to which Joker decided that he should attempt to earn something. Joker opposed Peter's idea of stealing, stating that he had a feeling it would be wrong to use stolen money "this time". Joker, Beast, Dagger, Peter, Wendy and Jumbo then proceeded to work on manual chores earnestly all night long in order to earn a single coin for Doll. They were relieved to see they made it on time as they placed it beside her whilst she was sleeping. The next morning, an oblivious Doll showed off her coin to them, stating how happy she was that they could eat bread with it and an exhausted but happy Joker laughed along with her. However, in the belief that the Tooth Fairy would give her more coins, Doll later attempted to take out more teeth that weren't wobbly, to the dismay of the others.
One day, while sitting under a tarp in the rain, Baron Kelvin found them and took them in. Joker called living at the manor "heaven." After some time, they decided to start a circus, and Joker assigned them stage names; it is understood that Joker is a stage name—however, not even the Grim Reapers have a record of his birth name.
Sometime later, Joker tried to help Kelvin with his obsession with Ciel Phantomhive, such as when he relayed information of Ciel's assumed death and when he prevented Kelvin from attending Ciel's sacrifice.
At a circus show that Ciel Phantomhive and Sebastian Michaelis attend, Joker represents himself as the ringleader. He runs the show, introducing the acts, and during Beast's act, he invites Sebastian down to participate. Sebastian soon gets bitten by the tiger, to the horror of both Joker and Beast. After the show, Joker hunts Sebastian down, and insists on taking him to the first-aid tent to have his wound checked out.
When Beast entered the tent to have her prosthetic leg examined by Doctor, Sebastian takes an interest in her limb and grabs it to look at it more closely; this upsets Beast and Dagger, who attack him with whips and knives respectively. However, when Sebastian is able to evade all of the attacks, Joker intervenes and states that he would like to scout him, to Beast's chagrin. Sebastian accepts the offer, and the next day, he returns with Ciel to take the entrance exam. When Ciel eventually passes, Joker gives them stage names, takes them both on a tour of the tents and leaves them in the practice tent. At the end of the day, he assigns tent mates, pairing Ciel with Freckles and Sebastian with Suit.
The following evening, they have another performance, and Ciel and Sebastian seize the opportunity to look through the first-string members' tents. However, Joker stops them, because Wendy hurt her ankle, and he needs Sebastian to stand in for her. Ciel develops an alternate plan and is able to look through all of the first-string members' tents during the performance, including Joker's, where he finds a piece of paper with his name and a brief history. Joker, along with Jumbo and Peter, learns from Snake of their invasion into their tents, and Joker decides to go see "Father" about what to do. While leaving, he runs into Beast, who asks him to run away with her, but he says it is impossible. Joker then gives her his scarf and tells her to go to bed.
Joker arrives at Kelvin's mansion and gets ready to see him. Kelvin is disappointed to learn that Joker does not have Ciel with him, and Joker announces they seem to have been marked by the Scotland Yard. When he elaborated, Kelvin is excited, because he is certain that Smile and Black are actually Ciel and his butler. Kelvin orders him to prepare a feast for their expected visit, but Joker is worried about the other first-string members. Angry with his disobedience, Baron passively threatens him with his brothers and sisters still at the workhouse, and Joker is forced to comply to his desires.
That evening, Joker welcomes Ciel and Sebastian into Kelvin's manor and introduces them to Kelvin. While eating dinner, Kelvin commands him to put on a circus performance for Ciel, which involves using the untrained, kidnapped children as the performers. Because they are inexperienced, their acts result in their gruesome deaths, which noticeably disturbs Joker. When Ciel expressed his disgust, Kelvin constrains Joker to clean it up. Ciel approaches Kelvin with a gun, and Joker is stopped by Sebastian from coming to the latter's aid. Kelvin orders Joker to put away his sword, and Joker remains in the custody of Sebastian.
They are then led to the basement by Kelvin, who reveals that he has turned the basement into a recreation of the day Ciel was sacrificed. Upset by his story, Ciel shoots him, and Joker tries to escape Sebastian by pulling a hidden knife out of his prosthetic arm. However, Sebastian cuts off part of his left arm and forbids him from disturbing his master. Joker pleads with Ciel for Kelvin's life, and discloses that the reason he acts at his bidding is because he needs Kelvin's help in order for them to survive. Ciel says he understands, but that is not going to stop him from "stealing his future." Joker proclaims that the other first-string circus members are visiting his manor that night, to silence all the witnesses, and hence stealing something precious from Ciel. Ciel is unconcerned, because his servants are his private army, and Joker quietly wishes for at least the first-string members to survive. He laments his past, which has led to this tragedy, and Ciel tells him not to cry so shamefully as the world is not kind to anyone.
Doctor then enters the basement and demonstrates that he can walk, much to Joker's surprise. He also reveals that the prosthetic limbs Joker, Dagger, and Beast wear were made from the bones of children. Joker was unaware of this, and is disgusted, questioning what Doctor saw them as. Later, after Ciel and Sebastian killed Doctor and Kelvin and set the mansion on fire, William T. Spears states that Joker died of blood loss on February 9, 1889.
- (To Ciel Phantomhive) "Looks like there's a touch o' truth to the saying that folks aren't always as they seem. Ye've got such a little body . . . yet your stage names are 'The Queen's Watchdog' and 'The Aristocrat of Evil.' Must've 'ad a rough go of it, eh, Smile?"
- (To Ciel Phantomhive, regarding Kelvin) "Please don't kill him! Despite what he is, he saved us! We were abandoned by our parents and our country. He saved us from the fear of starvation. Many brothers and sisters of ours are still at the Workhouse. If he dies, we can't live on."
- (To Ciel Phantomhive) "Do you know why we have never been caught while kidnapping all those children? It's because every witness has been killed. We circus members are professionals. We eliminate anyone who crosses our path while on a mission, no matter who or what."
- "I wonder... what we should have done. Like the nursery rhyme, we were 'capable of playing only one song.' But if... if we had been born in another country... our selves... our bodies... wouldn't have been like this."
- According to the official Kuroshitsuji's character popularity poll, Joker is the eleventh most popular character in the series, with 168 votes.