'The Batman' actor wrapped his head in cling wrap to play the Riddler. He warns fans not to do the same if they dress up as the villain.

• Paul Dano wrapped his head in cling wrap to play the Riddler in "The Batman."
• Dano didn't realize he wouldn't be able to sweat with it on. Holes needed to be punctured in it.

Paul Dano's more serious take on the Riddler in "The Batman" wears a more practical outfit than past versions of the character as he carries out murders in Gotham City.

But you may have missed that the character also wraps his face tightly in cling wrap, an idea Dano came up with himself.

"I thought it would be kind of scary and weird," Dano said in the film's production notes. "[Director] Matt Reeves loved it; he loved anything that was upsetting or disturbing for the character."

During an appearance on "The Tonight Show" with Jimmy Fallon, Dano elaborated on the costume choice, saying he was trying to come up with a way for the character to not leave DNA at a crime scene while carrying out murders.

"He still needs to be able to go out in the day, so I couldn't shave all the hair off my body," Dano said. "So I had this idea of like wrapping myself in — I have to call it cling wrap because I think the Saran people don't want any legal association with my Riddler."

"I wrapped myself in cling wrap, which kind of looks scary with the light," Dano continued. "I thought, 'OK. Now, I'm not going to shed any hairs here on these crime scenes."

However, Dano said he didn't realize that he wouldn't be able to sweat with the cling wrap wound tightly around his face.

"The first day of filming, about an hour in, I just start to see white and colors," Dano said, adding he didn't want to cause a stir on set. "It's day one so you don't want to be the actor who's like, 'I've got a little headache here.'"

"You can't sweat. That's the issue. It's like going back inside of you," Dano said of the difficulties the cling wrap presented.

In an interview with The Hollywood Reporter, director Matt Reeves said he told Dano they should rethink the idea after noticing his face was "beet red" after removing the mask.

Dano insisted on moving forward with the plastic wrap, but the team came up with a fix.

"The next day, we just started to poke some holes in the cling wrap," Dano told Fallon. "My head could breathe. Things got a little better."

Dano cautioned that any cosplayers or fans deciding to dress up as his iteration of the character shouldn't do what he did.

"I might as well take this opportunity to offer a disclaimer to any Halloween costumers or cosplay fans out there. Maybe skip the cling wrap," Dano suggested.

You can watch Dano discuss his costume choice starting around the 3:25 mark below.