Joker: Folie à Deux’s set pictures reveal a first look at Lady Gaga’s Harley Quinn costume, and it is quite different from recent Harley Quinn adaptations. Though Joaquin Phoenix’s return as the Joker in Joker 2 was already enough to justify the sequel, the addition of Lady Gaga as Harley Quinn makes Folie à Deux even more exciting. Like Joker (2019), Folie à Deux will not have any ties to the DC Universe – it is a DC Elseworlds film.
Lady Gaga is not replacing Margot Robbie as Harley Quinn. Whereas Robbie played Harley Quinn in the DCEU, Gaga’s Harley will be part of a self-contained world that will not crossover into other DC properties. Though not much has been revealed about Harley Quinn’s role in Folie à Deux, the first look at Lady Gaga’s Harley Quinn costume tells a lot about this new version of the character.
Lady Gaga's Harley Quinn Costume & Makeup Is Very Different To Margot Robbie's 
Lady Gaga’s Harley Quinn look is quite different from Margot Robbie, which by itself was not like anything in either the DCAU or the DC Comics. Whereas Margot Robbie’s original Harley Quinn look was a mixture of the Arkham games Harley and musician Debbie Harry, Lady Gaga’s Harley Quinn costume is a more grounded, simpler take on the character that perfectly fits the realism of the Joker universe. Gaga’s Harley wears a vibrant scarlet jacket on top of a white shirt with black diamonds in it, and the eye makeup evokes Joaquin Phoenix’s Joker look. It is important to notice that Robbie's DCEU Harley Quinn has had multiple costumes already.
Essentially, Lady Gaga’s Harley Quinn costume went for a red and black color scheme – which is closer to Harley Quinn’s classic look – whereas Margot Robbie’s Harley Quinn originally went for pink and blue. It was only in The Suicide Squad that Robbie’s Harley costume was mostly red and black, although Harley Quinn did appear in her classic jester suit during Suicide Squad’s Joker and Harley montage. It must also be noticed that Margot Robbie’s Harley Quinn fell into a vat of acid and that her pale skin does not stem from makeup in-universe. Gaga’s Harley, on the other hand, is wearing similar makeup to Phoenix’s Arthur Fleck.
Which DC Comics & Shows Is Lady Gaga's Harley Quinn Costume Inspired By? 
By going for the red and black color scheme, Lady Gaga’s Harley Quinn costume is evoking Harley’s original look from Batman: The Animated Series. Harley Quinn was created by Paul Dini and Bruce Timm for Batman: The Animated Series, and what initially was supposed to be a background villain in a Joker-focused episode is now considered one of DC Comics’ most important characters. That said, Gaga’s Harley Quinn costume is not that similar to Harley’s red and black jester suit, although the colors are an intentional callback. The diamonds in Harley’s shirt and in her eye makeup also reference Harley’s original DCAU costume, which had diamonds drawn in it.
