There is no substitute for the real Rachel Weisz. So said Tom Hiddleston, on hand at the Variety Studio in Holt Renfrew in Toronto on Monday to promote Terence Davies’ romantic period drama “The Deep Blue Sea,” based on Terence Rattigan’s play about a judge’s wife caught up in an extramarital affair with an Air Force pilot.

“The best thing about ‘The Deep Blue Sea’ was acting with a real Rachel,” Hiddleston said. “In some of the stuff I’ve done (“Thor”), you’re surrounded by a green screen or feeding lines to a mark on a map box or a tennis ball taking the place of a computer-generated image of a monster or something. There’s no substitute for the real thing.”

The “real thing” herself doesn’t mind a little pretending; she’s filming Sam Raimi’s “Oz: The Great and Powerful.”

In “Sea,” Weisz said, “we’re imagining we’re in 1950s London. Right now I’m imagining I’m in the Emerald City. It’s all an imaginative process. There are more similarities than perhaps you would think. … It’s just a different muscle you learn to exercise. It’s challenging, but not uninteresting.”

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“Your Sister’s Sister,” Lynn Shelton’s eagerly awaited comedy follow-up to her Sundance hit “Humpday,” brought the writer-director and stars Emily Blunt and Mark Duplass out to the Variety Studio on Monday.

Shelton recalled that “Sister” was based on the “kernel of an idea” Duplass said he and his brother Jay didn’t have time to direct but that he wanted to star in. The mostly improvised approach was similar to her last project, with actors working from a “half script/half treatment” book.

“We developed (detailed backstories for the characters) over the phone over the course of eight months,” Blunt said.

“It was a big intellectual bro-down for us, basically. We needed to look like we’ve been best friends for-e-ver,” recalled Duplass. “We’d slung enough fart jokes at that point, I thought, ‘We might pull this off.’ ”

“We were such fake buddies!” added Blunt with a laugh.

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The Variety Studio got off to a rockin’ start Saturday, when Soundgarden’s Chris Cornell was on hand to promote “The Keeper,” his original song contribution to Marc Forster’s “Machine Gun Preacher” from distrib Relativity Media.

Cornell wrote the song after reading Jason Keller’s script, based on the true story of drug dealer turned Sudanese child rescuer Sam Childers (Gerard Butler). Ironically, it didn’t help his writing process — it made things tougher.

“The arc of the story is so huge (and) incredible,” Cornell says. “Just the beginning — how he gets to the point where he can transport himself to the south Sudan and start doing what he became famous for — is a book or movie (in itself). Also, that’s never been my life or experience. (Except) some parts of it — the ‘I ride a motorcycle and do too many drugs’ part — I’ve bumped my head against that before,” he laughed. “But I wrote that song already.”