TORONTO -- Rachel McAdams hands it to Robert Downey Jr. for giving marquee actors more reason to jump aboard Hollywood superhero movies.

The London, Ont.-born actress says it was Downey's role as Tony Stark in Marvel's "Iron Man" series that pushed some performers, who might've never considered donning a mask and cape, to rethink their stance on big-ticket franchises.

"He paved the way to how much the audience was craving fully-formed, fully-fledged human beings," she said in a recent interview.

"They've become really rich worlds."

McAdams is one of the latest inductees into the Marvel cinematic universe with "Doctor Strange." It's a sci-fi adventure grounded in mysticism with a hint of influence from "The Matrix" and "Inception." It hits theatres on Friday.

She plays Christine Palmer, the emotional support for Benedict Cumberbatch's title character, a genius neurosurgeon who becomes a master of the mystic arts after a disfiguring car accident leaves him on a desperate search for answers.

Both actors once seemed unlikely candidates for high-concept fantasy. McAdams is coming off her Oscar-nominated performance in "Spotlight" while Cumberbatch vied for a golden statue himself in the 2014 drama "The Imitation Game."

McAdams, who admitted she was never much of a comic book reader growing up, said she was attracted to "Doctor Strange" after director Scott Derrickson pitched her the idea over lunch. It was the first time she'd been offered a superhero franchise role "flat out," which was intriguing to her in itself.

Derrickson had mostly dabbled in writing and directing horror flicks, with films like "Sinister" and "Deliver Us From Evil" under his belt, so making a Marvel movie laced with Dali-esque visual effects was a serious departure.

"It was incredibly ambitious what he was trying to do," she said.

"There's spirituality and we're dealing with a new kind of universe with magic and the occult -- there was some real depth to it that drew me in."

McAdams described her role as "an amalgamation of a couple of characters" from the original comic book, although avid Marvel comic readers will instantly recognize her as one of the three females leading the "Night Nurse" series.

On the printed page, Palmer's character eventually crosses paths with X-Men's Nightcrawler.

McAdams won't talk about whether her character will follow a similar trajectory in the films. Marvel is notorious for making their actors take an oath of silence about where and when characters return to the screen.

"There's not much I can say without spontaneously combusting before your eyes," she joked.

"Generally if the film's successful they tend to carry on, so hopefully people like this and the stars align again."

McAdams said "Doctor Strange" has already opened her eyes to a new world of literature.

She's particularly fond of Canadian graphic novelist Jeff Lemire, who wrote the "Essex County" trilogy and was recruited by Marvel for "Extraordinary X-Men" and other comics. She also enjoys British cartoonist Neil Gaiman, writer of "Signal to Noise" who later joined the ranks of DC Comics.

"I get really swept away in those," she said. "But it's come later in life for me."

If she's back for another Marvel movie, McAdams will be completely in her element, she said.

"It's the ultimate in make believe," she said, "which is why we all got into this in the first place."