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, but brushed it off for the time being. After a chance encounter with fellow outsider Ryuji Sakamoto over their lecherous 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, 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 Persona is Arsene, based on the literary gentleman thief Arsène Lupin.
Joker is one of the many playable characters in Super Smash Bros. Ultimate. He was confirmed to appear in the game on December 6th, 2018 during The Game Awards 2018. He is the first DLC fighter to be part of the Fighters Pass Vol. 1. 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.
- Joker is the only character to have more than one victory theme in the same game. He is also the second character whose victory theme plays continuously, replacing the results theme; after Cloud.
- Joker is the only character in the series to have two full-fledged trailers for the same game.
- Joker is the third Sega representative in Super Smash Bros., after Sonic and Bayonetta.
- Joker is the third character featured in the Super Smash Bros. series to appear in M-rated games, the other two being Solid Snake and Bayonetta.
- Joker's English voice actor is Xander Mobus, who also voices the announcer, Master Hand, and Crazy Hand in Super Smash Bros. 4 and Ultimate. This marks the first time that an English voice actor for any one of those characters voices a playable character.
- His Japanese voice actor, Jun Fukuyama, also provides the Japanese voice of Roy.