The brief video Phillips posted -- which Warner Bros Pictures retweeted -- shows Phoenix as Arthur Fleck, unsmiling and wearing rumpled clothes.
Colored light flashes across his face offering a hint of the Joker's signature clown makeup.
The video stops with Arthur grinning widely, lips and eyebrows painted red, on a pale, white face.
Phillips released the first photo of Phoenix as Arthur, the man who will ultimately become Batman's greatest foe, on Sunday.
Shortly after that, the film studio offered details about the storyline, explaining, "Phillips' exploration of Arthur Fleck, a man disregarded by society, is not only a gritty character study, but also a broader cautionary tale."
Filming is now underway. Co-starring Robert De Niro, Zazie Beetz, Bill Camp, Frances Conroy, Brett Cullen, Glenn Fleshler, Douglas Hodge, Marc Maron, Josh Pais and Shea Whigham, the movie is set for theatrical release Oct. 4, 2019.