Leto interview: "The Joker feeds off resentment. The more resentment, conflict, and enemies he gets, the more fulfilled he feels.
Idk if scans are allowed so can't post source
Robbie tells us that she never had a problem with Letos special deliveries. "I loved that stuff. I mean, Jared was doing half of my work for me. Harleys very much part of this relationship, and to have such commitment on the other half made my job a thousand times easier and a thousand times more fun. It keeps you on your toes, I dont know whats going to happen when we go on set, I have no idea what hes going to do. Its so exciting to act opposite that."
"It really brought [things] to life for us, adds Delevingne. Going from us rehearsing from the page to going to such visceral things [that] you can feel and touch, in your face, like
holy shit! Its like interactive theatre.
Indeed, one gift from Leto is credited with forging the Squad itself. While Ayer got the actors working on bonding and developing their characters, Leto stayed separate. However, on one occasion he did make his presence felt, as Jay Hernandez remembers. One of Jokers henchmen came into the rehearsal space, and when that happened it galvanised us; something happened, he tells us. The Suicide Squad was born! laughs Smith.
He just burst in. 'What the fuck? I know weve got security outside!"
"He had a dead pig, and threw it down on the table and said, 'Heres a present froth Mr J, Kinnaman picks up. He had the slit throat with the tongue sticking out, interjects Delevingne. And me and Jai looked at each other like, 'Weve got to do somethig, man! laughs Kinnaman. Hed already walked out so we ran down the corridor and dragged him back into the room. He was like 'Guys, its over, its over. 'Its not over! We pulled him in and everybody jumped him. We tied him, took a picture, put the pig around his shoulders and put an apple in its mouth. 
That was [Letos] gift, and it was really special and mind-blowing and fucking awesome, concludes Hernandez. When it happened, its like everybody turned and we were instantly like, what are we doing? What the fuck are we doing? 'Weve gotta retaliate, weve got to do something remembers Robbie. It changed everything. The final drop in the cauldron, adds Delevingne gleefully.
