'Grey's Anatomy' stars Ellen Pompeo, T.R. Knight, Justin Chambers and Chandra Wilson

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Viewers can't get enough of the hit ABC medical drama Grey's Anatomy—its vital signs are off the charts! Freakish medical conditions, sleep-deprived doctors, complicated romances and a healthy dose of sex bring in 20 million viewers every week.

The cast includes Ellen Pompeo as surgical intern Meredith Grey and Patrick Dempsey as Meredith's love interest, neurosurgeon Derek Shepherd—affectionately known as "McDreamy." For the first time, Ellen is taking The Oprah Show behind the scenes to reveal Seattle Grace Hospital's best-kept secrets!

To keep operating room scenes realistic, Ellen says the show hires a team of real-life nurses who make sure the actors are using the right surgical instruments. Chandra Wilson, who plays Dr. Bailey, reveals another trick of the trade—chitlins are used as intestines on the operating table!

The cast members admit that their secrets aren't all about the medicine. One little known fact is that actor Justin Chambers, who plays cocky bachelor Alex Karev, has been married for over 10 years and is the proud father of five children! Actress Katherine Heigl, the model-turned-doctor Izzie Stevens, is a total bookworm, reading a book a day on set during downtime. And T.R. Knight, the sweet and self-conscious Dr. George O'Malley, is the clown of the group—he keeps everyone on the set in stitches!