Rob Lowe could have been scrubbing in as "Grey’s Anatomy‘s" Derek Shepherd, aka McDreamy. But during a podcast interview with Marc Maron, Lowe confessed that he turned the role down — and “that’s probably cost me $70 million,” he joked.

After watching the pilot, though, Lowe believed he’d made the right decision: “When they started calling the handsome doctor ‘McDreamy,’ I was like, ‘Yeah, that’s not for me.'”



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Shortly before she auditioned for "Lost" (for the role of Kate, actually), Yunjin Kim looked to scrub in at ABC’s new medical drama, "Grey’s Anatomy". “I did not audition for [Cristina Yang], it was for Izzie,” Kim told EW.com. “And I got a callback.”

Kim wound up wowing "Lost" boss J.J. Abrams enough to not play Kate but have the role of Sun created for her. And while she didn’t at first cancel her "Grey’s" callback, she ended up skipping it. (And the role of Izzy of course eventually went to Katherine Heigl.)

https://tvline.com/lists/tv-actors-almost-played-different-roles/yunjin-kim-greys-anatomy/