The Rock Revealed How He Made 'Black Adam's Biggest Surprise Happen & Shots Were Fired (VIDEO)

Dwayne Johnson's anti-hero has to wait 5,000 years before he's unleashed on the world in Black Adam, and it feels like the Rock had to work nearly as long to pull off the biggest surprise of the film.

We're not going to spoil the surprise, but Johnson was more than happy to tell us how it all came together during a recent visit to Toronto.

"It was years," Johnson told Narcity on Thursday, during a stop on his Black Adam world tour.

He added that the biggest hurdle wasn't convincing certain people to be part of it. It was getting the bosses at Warner Bros. on board.

"Six years we first started talking about this, and they kept saying no," he said, before throwing a bit of shade at the studio's old bosses, many of whom have left in recent years.

"Now that leadership isn’t there anymore," he said. "We're ushering in a new era in the DC universe, and we usher out an old era in the DC universe too."

'The Rock' on being 'Black Adam' interview. Narcity | Youtube

Black Adam executive producer Hiram Garcia, who has worked with the Rock since his first film in 2002, says it took a massive effort to bring everything together for the film's biggest surprise.

"One of the producers has been working that diligently for six years and (on) their relationship with that person," he said. He added that he and Johnson had a "relentless, non-stop conversation" with Warner Bros. to make it happen.

"We would not take no for an answer," he said. "We got 'no' several times. We took a beat, re-taped our gloves, maybe took off the gloves (...) went bare-knuckle and went back to it. And for us to finally get it, it was such a special moment."

The Black Adam character hasn't been a household name up until this point, but as The Rock has pointed out many times, he's nearly as strong as Superman.

Henry Cavill last played the Man of Steel on screen, although his future with superhero movies has been a big question mark in recent years.

But there's one big difference between Black Adam and Superman, as Johnson told fans in Toronto on Thursday.

"Black Adam will kill your a** just like that."

The character actually started as a villain for Captain Marvel/Shazam back in the 1940s, and that's left fans wondering if Johnson and Shazam star Zachary Levi will meet in the future. The first two Shazam movies were shot in Toronto, so we asked if the Rock might be back in town for a crossover one day.

"We want him to cross paths with all DC heroes," Garcia said. "We know the history between those two characters, and our goal is to eventually make that happen."

Black Adam opens in theatres everywhere on October 21.