AceShowbiz - Actress Ellen Pompeo was left with little choice but to step in to shoot a "dangerous" "Grey's Anatomy" scene years ago after her stunt double was knocked out.

The star was asked to reshoot a bomb explosion scene for season two after her stunt expert hit her head so hard, she needed emergency medical treatment and, even though Ellen didn't feel comfortable doing so, she agreed.

The actress, who plays lead character Dr. Meredith Grey on the hit drama, revealed the behind-the-scenes secrets on Twitter after a fan shared a clip from the 2006 episode "As We Know It", which is set to be rebroadcast in the U.S. next week (begs10May21).

The instalment featured a man who walked into the hospital with a bomb inside of him, with Grey forced to hold onto the patient to prevent the weapon from exploding. However, the subsequent detonation killed a bomb squad member, played by Kyle Chandler, and caused Grey to be thrown backwards and onto the ground at great force.

The fan captioned the short video, "All i'm going to be able to think about is how hard @EllenPompeo hit her head on that floor (sic)."

Ellen spotted the tweet and spilled all in response, "That was actually a stunt double that got a concussion and had to go (to) the ER (emergency room)."

"Well of course the director insisted I do it after the professional got hurt of course they would ask me to do it and of course being the people pleaser I was ... I said yes knowing they would use the take where she hit her head anyway because that looks so dramatic (sic)."

Ellen admitted she felt "uncomfortable" shooting the stunt but didn't think she was in a position to say no.

She continued, "The lesson here ladies is this... don't do things that make you uncomfortable because you're afraid people will see you as difficult. Trust me they are going to see you as difficult no matter what you do!"

"I'll also add ..it was about 230am and we'd been shooting easily 15 hours at that point I was physically and mentally exhausted from shooting the other parts of that scene and knew it was dangerous and I still did it anyway..not to be a hero... to not be a 'problem' (sic)."

However, she also insisted the experience was a great learning curve in pushing herself to make the show as good as possible.

Ellen concluded, "But also in an effort to do whatever was necessary to make the show great... all worthwhile lessons. There is a lot of value both in working hard and making mistakes (sic)."