In the series, Kidman’s character comes to harrowing realisations about the behaviour of her oncologist husband, Dr Jonathan Fraser (Hugh Grant).
Speaking to Marc Maron on his WTF podcast, Kidman said: “On The Undoing it kind of happened where I was suddenly in this place of... there was sort of a disquietedness to my personality, where I was uneasy and there was duress on who I was.”
The Destroyer star said that she even became “really sick” during production on the series.
“I went down for a week,” she claimed, “because your immune system doesn't know the difference between acting and truth when you're doing them.”
Elsewhere on the podcast, Kidman also described the moment she learned of the death of the legendary filmmaker Stanley Kubrick, who directed her alongside then-husband Tom Cruise in 1999’s Eyes Wide Shut.
She revealed that Kubrick had faxed her the night before she learned of his death, asking her to call him, but she didn’t.
“I just started screaming. I collapsed on the ground,” she said. “I was that close to him.
“I have a huge fear of phone calls in the night now,” she continued, “because I've received a number of them with that sort of news, my father included.”
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