George Clooney is just one of the many celebs who have stopped by the “Big Brother” household.

The “ER” alum was on the same lot as “Big Brother” when Executive Producer Allison Grodner got a call from an editor asking if he and a friend could come for a tour.

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“The peak experience of my life was giving George Clooney a tour,” Grodner told the Entertainment Weekly‘s recap of “Big Brother” “But First”.

“He was on the lot cutting a movie many, many years ago. His editor at the time was a super fan of the show. He called and said, ‘Can I stop by and I want to bring a guest.’ The guest was George. I’ll admit, I went home and changed immediately.”

And while Clooney wasn’t familiar with the reality series, “he was one of the nicest celebrities I’ve ever met,” she recalled. “He was really fascinated. Walking around behind the scenes was something that was intriguing to him. That was a big one. That was a highlight.”

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Although the most shocking part of this story is that Grodner never told any of the houseguests that one of the biggest celebrities in the world was watching them from behind-the-scenes.

You can catch “Big Brother” on Global. Starting Wednesday, July 10, Big Brother moves to Wednesdays and Thursdays at 9et/pt, while the Sunday broadcast will remain at 8et/pt.