The first trailer for Joker: Folie à Deux, the musical sequel to Joker starring Oscar winners Joaquin Phoenix and Lady Gaga, has been revealed.

The sequel sees Phoenix return as Arthur Fleck, the titular aspiring standup comedian turned villain, and Lady Gaga as Dr Harleen Quinzel, a psychiatrist assigned to treat Fleck at Arkham Asylum, who falls in love with him and becomes his accomplice Harley Quinn.

The title is a reference to a psychiatric syndrome in which a delusional state is shared by two people.

Unlike Joker, Joker: Folie à Deux will be a musical and is expected to include 15 numbers, Variety reported, with most of them being covers of pre-existing songs, including That’s Entertainment from the 1953 musical The Band Wagon, which was also famously sung by Judy Garland. The trailer features the 1965 song What the World Needs Now Is Love.

Joker: Folie à Deux also stars Zazie Beetz, Brendan Gleeson, Steve Coogan and Catherine Keener and is directed by Joker director Todd Phillips, who originally said the first film was “always pitched it as one movie” but would be interested in making more if Phoenix was involved.

Phoenix, who won his first Oscar for his performance as Fleck, has been enthusiastic about the role, telling Rolling Stone: “I can’t stop thinking about it ... if there’s something else we can do with Joker that might be interesting”, adding that he believed there were “endless … possibilities of where we can go with the character.”

Joker made box office history when it was released in 2019, becoming the first R-rated film ever to gross over USD$1bn. It won the Golden Lion at the Venice international film festival and was nominated for 11 Oscars, winning two.

Joker: Folie à Deux will be released in cinemas on 4 October.