George Clooney rose to fame in the 1990s starring on the television show “ER,” and since leaving the popular program in 1999, he has gone on to become one of the most A-list stars in Hollywood.

Unlike many others stars, it seems that Clooney has not forgotten his roots, however, as he just shocked his fans when it was announced that he will be reuniting with the cast of “ER” for a special cause.

Entertainment Tonight reported that “Stars in the House” creators Seth Rudetsky and James Wesley took to Twitter this week to announce that the cast of “ER” will be reuniting for a special Earth Day episode that aims to benefit the Waterkeeper Alliance, an organization that works to ensure every community worldwide has drinkable, fishable and swimmable water.

Clooney (Doug Ross) will be joined by castmembers Julianna Margulies (Carol Hathaway) and Noah Wyle (John Carter) for the special reunion episode. Others who will be taking part in this include Gloria Reuben (Jeanie Boulet), Laura Innes (Kerry Weaver), Anthony Edwards (Mark Greene), Alex Kingston (Elizabeth Corday), Goran Visnjic (Luka Kovac), Paul McCrane (Robert Romano), Ming-Na Wen (Jing-Mei Chen), Laura Cerón (Chuny Marquez), Yvette Freeman (Haleh Adams), Conni Marie Brazelton (Connie Oligario), and CCH Pounder (Angela Hicks).

The reunion episode is set to premiere on Thursday, April 22, at 8 p.m. ET., and it will stream on People‘s social platforms on Facebook, Twitter, and YouTube, as well as on PeopleTV’s Facebook and Twitter.

Reuben issued a brief statement talking about how much this cause means to her.

“I am absolutely thrilled to be reuniting with my ER family for a cause that is so close to my heart, and so grateful to Seth and James for allowing us to use their incredible platform to do so,” she said. “I’ve been involved with Waterkeeper Alliance for fifteen years, representing over 350 community-based Waterkeepers around the globe, and the work that they do is beyond comparison. We must continue to fight for clean water not just on Earth Day, but all year round!”

This comes a month after Clooney revealed that his wife, human rights attorney Amal Clooney, had just started watching his old “ER” episodes, and that she was not a fan of his character.

“My wife is watching them now,” he said. “And it’s getting me in a lot of trouble because I’d forgotten all of the terrible things [his character Doug Ross] was doing picking up on women.”