“Folie à Deux” does neither. Taking a cue from the last scene of “Joker” — a psych evaluation where Arthur hears Frank Sinatra’s “That’s Life” in his head and starts to sing along — the film is basically one long drawn-out courtroom drama, interrupted by musical numbers (old standards, most of them sung in Arthur’s head).

Folie à Deux might be getting a mixed reception among audiences and critics, a new theory suggests that you might have got the meaning of the sequel all wrong. One TikToker has taken a deep dive into the film,