Clayton Davis Senior Awards Editor The Joker and Harley Quinn are set to serenade audiences in “Joker: Folie à Deux,” but if, and how many of original songs will be included in the film, is a mystery. Insiders privy to filming and early versions of Todd Phillips’ eagerly awaited sequel to “Joker” tell Variety the movie leans heavily towards being “mostly a jukebox musical,” as it integrates at last 15 reinterpretations of “very well-known” songs. One is said to be “That’s Entertainment” from the 1953 musical “The Band Wagon,” famously associated with Judy Garland.