'Grey's Anatomy' Cast Reacts to Surpassing 'ER' as Longest-Running Medical Drama in TV History (Exclusive)

'Take that, George Clooney!'

Grey's Anatomy is making TV history on Thursday night. 

Thursday's episode of the ABC series makes Grey's the longest-running medical drama in TV history, surpassing E.R. During a visit to the show's set in January, stars Ellen Pompeo, Jesse Williams, Camilla Luddington and more reacted to the news -- some with more confidence than others. 

"Take that, George Clooney!" Giacomo Gianniotti joked while chatting with ET's Leanne Aguilera. "Since I joined the show, we've hit so many different milestones in terms of how many episodes, how many seasons we run, and so now to also take this place is always really exciting."

"I feel like every season we are breaking barriers and we are breaking records," he added. "It's awesome."

Pompeo, who has starred as Meredith Grey since the show's very first episode in 2005, said the show's new milestone is a big "pat on the back" to the entire cast and crew. 

"TV has completely changed, and there's so much great TV out there, so being able to compete with all these super cool cable shows and amazing actors doing these shows, to be able to still have our position, and keep our ground as the number one network drama on ABC,  think is really amazing," she gushed. 

"I'm not great at patting myself on the back, but I'm just going to give us all a great big pat on the back," Pompeo continued. "Because in this landscape, its really hard to compete, and were doing it. We're staying afloat in the midst of all these shows, this revolution of television. We're still here. And I think its pretty cool. "

The 49-year-old actress said she doesn't remember shooting the pilot -- "It's all just a blur," she said with a laugh -- but Luddington does. The English actress revealed her very first scene was with Pompeo. 

"I remember it was just a scene with me and Ellen and I had like a page of medical dialogue that I got the night before. And I remember being so nervous that I think I screwed up the take like a hundred times," Luddington dished. "That scene actually never even made it into the episode, that's how terrible of a job I did that first day. That's what I remember -- being so nervous."

James Pickens Jr. remembers the series from the beginning, when 'there was no real 'star' in the show. "The atmosphere was really exciting, and it was uncharted territory for us," he said. "Little did we know, 332 episodes later, here we are."

"I'm really proud of Shonda [Rhimes] and the entire team," added Jesse Williams, who said he "mangled my audition" and asked Rhimes for a "redo." 

"I think my first scene was like a big group scene with a bunch of the original actors. It was Ellen and Sandra Oh and Katherine Heigl and a bunch of people," he recalled. "It was a little intimidating honestly, because I wasn't an actor. I had just moved here from Brooklyn. I had done a few jobs. I had maybe been acting for 18 months. I felt really, I felt really new and [said to myself], 'Just don't blow it, just don't blow it!'"

"I think [my favorite line] was Sandra Oh, Cristina Yang's line to Meredith, I'm gonna mangle it, but it's "he is not the sun, you are," Williams confessed. "It's a hell of a line." 

Pompeo also loved that Meredith-Cristina friendship. "I think [my favorite line] would have to be, probably, something between Sandra Oh and I. Maybe, 'You're my person.' Or when Sandra Oh says, 'Somebody sedate me!'"

And as characters come and go, Pompeo will always call the cast and crew "family." 

"We use the term family a lot. We throw that a lot. Sometimes its like a dysfunctional family. Because lord knows, drama comes with a lot of behind the scenes drama. I would say, its great to watch people become parents. And people get married. We have all those great moments," she shared. 

Grey's Anatomy airs Thursdays at 8 p.m. ET/PT on ABC.