For his Oscar-winning role in Dallas Buyers Club, Jared Leto lost 30 pounds, shaved his entire body, and refused to break character while filming the drama. And for his follow-up role in the upcoming Suicide Squad, Leto reportedly took his transformation into the iconic super-villain The Joker just as seriously.

In a new interview, Leto’s co-star Will Smith, who plays Deadshot, reveals that Leto completely disappeared into his character so much so that Smith still doesn’t know what Leto, the actor, is like in real life.

“[Suicide Squad] is insane,” Smith said in a Beats 1 interview Monday (via Complex). “I’ve never actually met Jared Leto. We worked together for six months and we’ve never exchanged a word outside of ‘Action!’ and ‘Cut!’ I literally have not met him yet. So, the first time I see him will be ‘Hey, Jared. What’s up?’ He was all in on the Joker.”

This summer, Leto and Smith’s Suicide Squad cast mate Adam Beach, who plays Slipknot, revealed that Leto sent out gifts in character as well.

“He sent [Margot Robbie] a nice love letter with a black box with a rat in it—a live rat,” Beach told E!. “It was beautiful. Then he sent bullets to Will [Smith] with a letter.”

According to Beach, Leto also sent the cast a video and a “dead hog.” Beach explained of the cryptic gestures, “Basically, what he said was, ‘Guys, I can’t be there but I want you to know I’m doing my work as hard as you guys. . . . The video he showed is in character. It blew our minds away. Then we realized that day, this is real.”

Leto isn’t the first character to disappear into the role of The Joker. While filming The Dark Knight, Heath Ledger kept a diary of the character. Ledger’s father, Kim, has since revealed, “He pretty well locked himself up in a hotel, in his apartment, for a month or so, to sort of galvanize the upcoming character in his own mind. . . . That was typical of Heath on any movie. He would certainly immerse himself in the upcoming character. I think this was just a whole new level.”

Ledger was awarded a posthumous Oscar for his chilling performance. Take a sneak peek at Leto’s Joker below in the Suicide Squad trailer.