In just a few short hours, Grey's Anatomy will make TV history.

When tonight's brand-new episode, the 15th in its 15th season, the beloved ABC drama will officially unseat ER as the longest-running primetime medical drama in American television history! With 332 episodes on the air (as of tonight) and at least 10 more on the way—Shonda Rimes' baby has yet to be renewed for a 16th season, though that seems like a mere formality at this point—the series has done something that, given the state of the current TV landscape, no show of its ilk will likely ever be able to top.

And what's more, it's done it with four of its original stars having run the entire damn marathon. OGs Ellen Pompeo, Chandra Wilson, Justin Chambers, and James Pickens, Jr. have stuck with the show through thick and thin, dramatic cast turnover and ill-conceived musical episodes, monumental pay raises—here's looking at you, Ellen!—and ratings resurgences, have starred as Meredith Grey, Miranda Bailey, Alex Karev, and Richard Webber, respectively, for the amount of time it would take an infant child to get their driver's permit. And at least one of them has every intention of seeing this thing all the way through to the end—whenever that may be.

During a visit to the Grey's Anatomy set last month while the cast filmed tonight's record-breaking season, we asked everyone if they thought they might have it in them to give Gunsmoke a run for its money and become the longest-running primetime drama ever. (That's 635 episodes, BTW.) And while Wilson was daunted by the prospect of challenging that other series—"I'd have to start over again to get to Gunsmoke!—she did admit that she's not going anywhere anytime soon.

"From a historical standpoint, would love to be able to say I was a starter and a finisher," she told us. "Actors don't get the opportunity to do that. I'd love to have the opportunity to put that personal star to put on my wall. I still enjoy Bailey immensely, I still learn from her. Until the wheels fall off, I guess."

Similarly, Pickens is hopeful that, when it comes time to film that final frame, Webber will be there standing tall. "To be at this point in my career and still have a job, hard to say maybe it's time to hang up," he told us. "I'd love it when it is time, I want to come in and turn off the OR light for the last time and have the show end there."

Meanwhile, Chambers is a bit cagier when it comes towards his commitment to the future. "Let's just do it season to season and go from there," he said. And Pompeo, well, her future on the series has remained quite the topic of conversation. After all, you can't have Grey's Anatomy without the Grey.

Speaking with E! News last week at the Sergio Tacchini pop up shop she hosted along with husband Chris Ivery, Pompeo told us that she didn't expect the show to end without her or her fellow OGs. "I think Shonda has said publicly that we'll decide collectively when to wrap it up, and we'll end the show together. I don't think she has any plans to continue the show without me, or any of the originals for that matter...but who knows, it's Hollywood," she said. "They can kick you out any time they want...but I think she has said publicly that we'd like to end this together, and her and I and the other three originals that are on the show...I think we'd like to sort of finish this together."

Of course, ER wasn't able to be so lucky. By the time the groundbreaking NBC series, which premiered in 1994, was signing off after 15 seasons, it did so without any of its original series regulars still in the gig. While nearly every OG—from George Clooney and Julianna Marguiles to Anthony Edwards and Eriq La Salle—popped us as a special guest in that final run of episodes in 2008-09, the show's last continuous original series regular, Noah Wyle, departed in 2005. (Sherry Stringfield would depart in 2006, though that was her second stint on the show, returning in 2001 after her initial departure in 1997.)

With Grey's' big day upon us, it got us thinking about the other ways in which the show stacks up against the series it's about to dethrone. Which show has featured more disasters? Which can claim the highest ratings? And which chopped more of its main characters' limbs? Check out our handy graphic below to see how Grey's Anatomy vs. ER by the numbers!

Grey's Anatomy vs ER, Infographic

Melissa Herwitt/E! Illustration

Over the years, Grey's and ER have also employed guest stars with some surprising connections to one another. To see what we mean, check out the list below!

ER, Greys Anatomy, Guest Stars, Leslie Bibb (ER)/Matthew Morrison (Grey’s)

NBC, Richard Cartwright via Getty Images

ER, Greys Anatomy, Guest Stars, Holland Taylor, Sarah Paulson

NBC; ABC

ER, Greys Anatomy, Guest Stars, Alexis Bledel (ER)/Edward Hermann (Grey’s)

NBC, Ron Tom/ABC via Getty Images

ER, Greys Anatomy, Guest Stars, Cress Williams (ER)/Kyle Chandler (Grey’s)

NBC, Peter 'Hopper' Stone/ABC via Getty Images

ER, Greys Anatomy, Guest Stars, Guillermo Diaz (ER)/Jeff Perry and Scott Foley (GREY'S)

NBC, Eric McCandless/ABC via Getty Images, Adam Taylor/ABC via Getty Images

ER, Greys Anatomy, Guest Stars, David Krumholtz (ER)/Christina Ricci (Grey’s)

NBC, Peter 'Hopper' Stone/ABC via Getty Images

ER, Greys Anatomy, Guest Stars, Keke Palmer

NBC; ABC

ER, Greys Anatomy, Guest Stars, Corey Stoll, Neve Campbell

NBC; ABC

ER, Greys Anatomy, Guest Stars, Octavia Spencer, Jessica Chastain, Chris Lowell

NBC; ABC

ER, Greys Anatomy, Guest Stars, Nasim Pedrad, Casey Wilson

Getty Images; ABC

ER, Greys Anatomy, Guest Stars, Martha Plimpton, Bernadette Peters

NBC; ABC

ER, Greys Anatomy, Guest Stars, Anna Gunn, Aaron Paul, Jesse Plemons

NBC; ABC

ER, Greys Anatomy, Guest Stars, Chris Pine, Chris O'Donnell

NBC; ABC

ER, Greys Anatomy, Guest Stars, Lucy Liu (ER)/Greg Germann (Grey’s)

NBC, Mitch Haaseth/ABC via Getty Images

ER, Greys Anatomy, Guest Stars, Josh Radnor

NBC; ABC

ER, Greys Anatomy, Guest Stars, Jeffrey Dean Morgan

NBC; ABC

ER, Greys Anatomy, Guest Stars, Don Cheadle and Chadwick Boseman (ER)/Tessa Thompson (Grey’s)

NBC, Gale Adler/ABC via Getty Images

ER, Greys Anatomy, Guest Stars, Jessica Capshaw

NBC; ABC

ER, Greys Anatomy, Guest Stars, Sally Field, Rita Moreno

NBC; ABC

ER, Greys Anatomy, Guest Stars, Dakota Fanning, Abigail Breslin

NBC; ABC

ER, Grey's Anatomy, Guest Stars, Alan Alda, Marion Ross

NBC; ABC

ER, Greys Anatomy, Guest Stars, Christina Hendricks, Elisabeth Moss

NBC; ABC

ER, Greys Anatomy, Guest Stars, Kirsten Dunst, Millie Bobby Brown

NBC; ABC

ER, Greys Anatomy, Guest Stars, Shiri Appleby, Jeanine Mason

NBC; ABC

ER, Greys Anatomy, Guest Stars, Kal Penn, John Cho

NBC; ABC

ER, Greys Anatomy, Guest Stars, Zac Efron, Demi Lovato

NBC; ABC

ER, Grey's Anatomy, Guest Stars, Mariska Hargitay, Mandy Moore

NBC; ABC

ER, Greys Anatomy, Guest Stars, Kyle Richards, Jamie Chung

NBC; ABC

Grey's Anatomy airs Thursdays at 8 p.m. on ABC. Meanwhile, ER's entire 15-season run is available to stream on Hulu.

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