Suicide Squad director David Ayer takes to Twitter to post a pic featuring Margot Robbie in the Jester Harley Quinn costume with Jared Leto as the Joker.
The scene was basically a cameo in Ayer's Suicide Squad movie and was briefly shown (watch below).
It's unknown why David Ayer tweeted out the image, other than it's really cool, but David Ayer is said to be directing the Gotham City Sirens movie featuring some of the female villains from the DC Universe also including Poison Ivy and Catwoman.
Regarding the Joker appearing in Gotham City Sirens, it has been reported Jared Leto is returning to the Joker role for Gotham City Sirens, Suicide Squad 2 and a separate Harley Quinn and Joker movie.
Gotham City Sirens has yet to be officially announced.