"I’ve never actually met Jared Leto," He told Zane Lowe on Beats 1 radio. "So we worked together for six months, and we’ve never exchanged a word outside of ‘action’ and ‘cut.’ We’ve never said, ‘Hello.’ We’ve never said, ‘Good day.’ I’ve only ever spoken to him as Deadshot and him as the Joker. I literally have not met him yet. ... He was all in on the Joker."
We'll find out whether Leto's performance warranted the "all in" approach when the movie hits theaters next August. Until then we'll just have to take Will Smith's reaction as proof that it was at least interesting. Skip to about 15:40 in the video below to hear him talk about the experience.