Julianna Margulies speaks about the abundance of chemistry between her and George Clooney on “ER” in a new interview with People.

The actress played Carol Hathaway on the hit medical drama after being cast as a guest star in 1994. She would go on to star in six seasons, with Hathaway and Clooney’s Doug Ross playing one of TV’s hottest on-screen couples.

Margulies says about the pilot episode, “I was supposed to die. I was just a guest star. I had to drive my cranky little rental car to Crenshaw at this abandoned hospital.”

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The star, who is set to release her new memoir, Sunshine Girl: An Unexpected Life, on May 4, met Clooney that day in the makeup trailer, “He could not have been kinder or sweeter.”

Margulies adds of the pair’s on-screen chemistry, “That can’t happen if you don’t have a crush on each other. And with George and me, it was so organic. I was just supposed to be a guest star, No. 39 on the call sheet. But he treated everyone the same.”

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Margulies, who married attorney Keith Lieberthal in 2007, says Clooney became her “mentor” during the production.

“I followed and watched how he conducted himself on the set. When you create an environment that people feel safe in, then you do your best work. And George taught me that,” she says. “I felt so safe with him. I mean, I never thought, ‘Well, why would I be in the bathtub and he’s coming in?’ I was like, ‘Okay, I’ll be in the bathtub. Yeah, great.'”