knows was an intimidating show for its guest stars. In , the 53-year-old actress tells  why people who guest starred on the beloved sitcom, on which she played Rachel Green, were "terrified" to do so

, a notable guest star, confirmed that he was nervous to appear on the series, but for a different reason than Aniston noted.

"[It's] really hard to come on a show where everybody's up to speed,"  during an April appearance on . "... I was scared to death [on ]. I had done  a long time before, but I hadn't done a sitcom.

And so, I was really nervous."

"Courteney helped a lot. Courteney's a big help," Selleck added of his frequent screen partner, . "But that group's an incredible group of friends. They obviously became friends in life as well as on the show. And it shows. It was a wonderful place to work."

During her "Actors on Actors" chat, Aniston also reflects on , noting that she and the other series' stars didn't expect "it to sucker punch us as hard as it did in the emotional gut."

"We just had the idea this is going to be so fun -- we’re going back to the sets exactly the way they were.

And literally, every single nook on a shelf was the same. It was so creepy," she says. "But each and every one of us, we walked in, it was just like, 'Oh!' [It was like] time travel."

During her "Actors on Actors" chat, Aniston also reflects on , noting that she and the other series' stars didn't expect "it to sucker punch us as hard as it did in the emotional gut."

"We just had the idea this is going to be so fun -- we’re going back to the sets exactly the way they were. And literally, every single nook on a shelf was the same.

It was so creepy," she says. "But each and every one of us, we walked in, it was just like, 'Oh!' [It was like] time travel."

Despite the heavy emotions the reunion brought up, Aniston tells Stan that she "wouldn’t change a lick of it."

"Every time we all get together, it’s just like no time has passed. We basically grew up together, and taught each other a lot," she shares. "We’re each other’s fall guy because the world was happening. We were exploding, and that kind of notoriety was sudden. And we were in these four walls doing the show, and this insanity is happening. And thank God we had each other, because we really couldn’t talk about it outside. It was before social media, so we still had some sanity."