Ellen Pompeo Says Her Reunion with Kate Walsh on Grey's Anatomy Will Be 'Very Emotional'

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Grey's Anatomy is not slowing down on the surprises — and Ellen Pompeo is here for it.

In an exclusive interview with PEOPLE, the actress — who launched her Tell Me with Ellen Pompeo podcast with Cadence13 on Wednesday — opens up about reuniting with former costar Kate Walsh for the upcoming 18th season of the ABC medical drama.

"Kate's so fun!" Pompeo, 51, says of the actress, who will reprise her role as Dr. Addison Montgomery this season. "She moved to Australia, so I really haven't seen her or hung out with her. I have so much affection and love for the original cast. We all went through something that only we can understand. So it's always just really fun and very emotional, to be honest. When any of the original cast members get together, we always start crying, and we're like, 'Why are we crying?' "

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"It's a sort of indescribable thing," she adds. "It's like, this show has been intense. It's definitely been a very, very intense experience. I don't think you'll ever talk to one person who's been on the show who has not had an intense experience, highs and lows. And I wouldn't change any of it, to be honest, maybe a few things. But for the most part, it's all made for a more meaningful journey. We created something so special together. That's a once-in-a-lifetime thing."

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Earlier this month, Walsh shared the news herself in a video posted on the Grey's Anatomy Twitter page.

"Well, well, well, would you look who it is. That's right, my loves, Dr. Addison Montgomery is coming back to Grey Sloan Memorial Hospital, and I'm so excited to be home again joining Shonda, Ellen and the rest of the incredible cast," Walsh, 53, said in the video, referring to series creator Shonda Rhimes and Pompeo.

RELATED: Kate Walsh Says She Would 'Absolutely' Return to Grey's Anatomy: 'It Changed My Life'

"This season — 18, whew! — just wait until you see what she has in store for you. The new season premieres September 30 on ABC," Walsh added.

Walsh joined the long-running medical drama in the season 1 finale as Derek Shepherd (Patrick Dempsey)'s estranged wife. She stayed on as the neonatal surgeon for several seasons before leading the spinoff series Private Practice, which aired from 2007 to 2013.

As for what's in store for Dr. Montgomery and Dr. Grey? Fans will have to tune in to see.

"The writers are trying to figure it out, and I try not to pressure them," Pompeo says of what's to come. "So it's a huge job they have. And that's really all I can say about it. So everyone just has to tune in!"

The crossover event between Station 19 and Grey's Anatomy airs Thursday, Sept. 30, on ABC, with the Station 19 season 5 premiere at 8/7c and Grey's Anatomy season 18 kicking off at 9/8c.