Joker (ジョーカー, Joker) is the codename used by the protagonist of Persona 5. Although Joker's civilian name is given by the player in Persona 5 itself, in the anime adaptation and spin-off Persona 5: Dancing in Starlight, he received the name Ren Amamiya (雨宮 蓮, Amamiya Ren); the manga adaptation also gives him the one-off name Akira Kurusu (来栖 暁, Kurusu Akira).
Ren Amamiya is the leader of the vigilante group known as the Phantom Thieves. After being falsely accused of assault, he was labeled a delinquent and moved to Tokyo, Japan to attend Shujin Academy as part of his probation while under the care of café owner Sojiro Sakura. While there, he discovers a strange application on his smartphone. After a chance encounter with fellow outsider Ryuji Sakamoto over their gym coach Kamoshida, they discover that the app is actually a conduit to a parallel reality called the Metaverse. This “cognition” is the manifestation of an individual’s twisted desires into a dream-like fantasy. In this case, Coach Kamoshida sees himself as the king of the academy and treats the rest of the students and faculty like slaves. Wanting no part in this reality, Ren rebels against the oppression of King Kamoshida and awakens his Persona, donning the mask and cloak of "Joker."
Joker is a user of a rare Persona ability known as the Wild Card, which allows him to hold multiple Personas at once. The Metaverse Navigator app and other aid in managing Joker's Personas is provided by Igor, the proprietor of the Velvet Room; a recurring feature of the Persona series. Igor warns Joker that ruin is imminent, and that his "rehabilitation," facilitated by himself and the twin wardens Caroline and Justine, is the only way to avoid this ruination.
Joker's initial Persona is Arsene, based on the literary gentleman thief Arsène Lupin. Joker awakens Arsene in order to save Ryuji in Kamoshida's palace. While attempting to escape, the pair meet a catlike creature named Morgana, who also possesses a Persona, Zorro, and mentors Joker in the use of Personas. Upon return trips to the palace, Ryuji awakens his own Persona, Captain Kidd, and the group is inadvertently joined by another of Kamoshida's victims named Ann Takamaki and her Persona, Carmen. Under guidance from Morgana, the group sends Kamoshida a calling card, announcing themselves as the Phantom Thieves of Heart, causing a treasure to manifest in the palace. The successful defeat of Kamoshida's Shadow, and theft of the treasure, results in a change of heart in the real Kamoshida.
Following this success, the Phantom Thieves pursue other targets, typically corrupt adults who victimize the young, gaining a large following and reputation. Over the course of their exploits, the group grows to include artist Yusuke Kitagawa (Persona: Goemon), student council president Makoto Niijima (Persona: Johanna), reclusive hacker Futaba Sakura (Persona: Necronomicon), heiress Haru Okumura (Persona: Milady), gymnast Kasumi Yoshizawa (Persona: Cendrillon), and briefly the detective Goro Akechi (Persona: primarily Robin Hood and formerly secondary Loki), who tries to stop the group in an attempt to arrest them. Ultimately, they end up exposing and ending a conspiracy to elect the corrupt politician Masayoshi Shido to the position of Prime Minister of Japan—who, through sheer coincidence, was the very same person who falsely accused Ren in the first place. Soon afterwards, they discover that the conspiracy was masterminded by the god-like being Yaldabaoth, who sought to merge the Palaces and the real world so it might seize control of both of them. After a long and desperate struggle, they banish the false god and free humanity from its control.
As a playable character
Main article: Joker (SSBU)
Joker was confirmed to appear in Super Smash Bros. Ultimate as a playable character on December 6th, 2018 during The Game Awards 2018. He is the first DLC fighter to be part of the Fighters Pass. He was released on April 17th, 2019 along with Mementos, its 11 music tracks, and several Persona series Spirits as part of Challenger Pack 1.
Masahiro Sakurai, in a video interview at Atlus, revealed that he had been a longtime fan of the Persona series ever since Revelations: Persona was first released on the original PlayStation. He played Persona 5 in his spare time and was continuously impressed by the stylish user interface. It was this initially strong impression that he aimed to capture the sense of style in Joker’s moveset and the mechanics of Mementos.