Paul Dano has opened up about his trouble sleeping while playing The Riddler in The Batman.

• READ MORE: ‘The Batman’ movie: release date, plot details, cast and everything we know

The actor is set to star in Matt Reeves’ new DC film about the caped crusader next month opposite Robert Pattinson as Batman/Bruce Wayne.

“There were some nights around that I probably didn’t sleep as well as I would’ve wanted to just because it was a little hard to come down from this character,” Dano told Entertainment Weekly, discussing a specific scene with Peter Sarsgaard’s character Gil Colson.

“It takes a lot of energy to get there. And so you almost have to sustain it once you’re there because going up and down is kind of hard.”

Dano went on to describe his experience covering himself in plastic wrap to get into character, as the Riddler would try to avoid leaving DNA evidence at his crime scenes.

“My head was just throbbing with heat,” Dano said, describing the moment he would take off the mask. “I went home that night, after the first full day in that, and I almost couldn’t sleep because I was scared of what was happening to my head.”

He added: “It was like compressed from the sweat and the heat and the lack of oxygen. It was a crazy feeling.”

Meanwhile, Pattinson revealed recently that he was asked to change his “absolutely atrocious” Batman voice when he was first cast.

“Everyone does this kind of gruff, gravelly thing, and I’m like, ‘I’m going to do the opposite, I’m going to go really whispery,’” he said.

“And I tried to do it for like the first two weeks and it just looked absolutely atrocious, and they told me to stop doing it.”

The Batman is released in cinemas globally on March 4.