'Big Bang Theory' cast reveals intimate secrets, reflect on final days on set

On Thursday night’s The Late Show With Stephen Colbert, the cast of The Big Bang Theory stopped by after the series finale aired to reminisce about their time on the show, and we learned some pretty intimate details during their visit.

“Did anyone ever have sex in their dressing room,” Stephen asked. “Show of hands.”

No one would fess up at first, but Kaley Cuoco instantly turned to Johnny Galecki and said, “You must have.” Guilty, he sheepishly raised his hand. Fans of the show remember that Cuoco and Johnny Galecki used to date, which they kept secret during the span of their relationship.

"It was such a huge part of my life and no one knew about it," Cuoco said. "It was a wonderful relationship but we never spoke a word about it and never went anywhere together. We were so protective of ourselves and the show and didn't want anything to ruin that. ... We knew how to keep it deep inside and never bring it on that set, ever."

While Cuoco and Galecki used to date, she insisted it was not her Galecki had sex with in the dressing room.

“And that did not include me,” she jokingly stated.

While what happens in Johnny’s dressing room stays in his dressing room, we also learned that’s true of the show’s props. Fans on Twitter have even been calling dibs on hot ticket items.

Unfortunately for fans, it looks like the set’s beloved props may not be going anywhere. Cuoco explained that it’s “been very serious about what people are taking.”

The cast confirmed that many items have even been bar-coded to ensure no one takes anything home with them.

“They bar-coded me,” Simon Helberg joked. “I can never work for anybody.”

The show made history during its 12 season run and is now the longest running multi-camera sitcom of all time. As it ends its historical run, fans of the show can travel to Washington, D.C., to see their favorite wardrobe looks.

“And a lot of it hasn't been announced yet,” Galecki explained. “But a lot of the wardrobe that Mary Quigley designed is going to the Smithsonian.”

Fans on Twitter were sad to say farewell to the show.

The cast was just as sad, revealing they even signed yearbooks during their final week. It really is so hard to say goodbye, but all good things must come to an end.

“We also did school portraits,” Cuoco explained. “So every single crew member, we did a portrait, which was hysterical. It was really cute, it really was from the beginning, a full 12 years of the book.”

Check out more from The Big Bang Theory at CBS.com.

Check out 'Big Bang Theory' series finale full of surprises — and fans can't handle it:

Read more from Yahoo Entertainment:

• Fans are having a hard time saying goodbye to 'Big Bang Theory'

• Howard Stern denies Sunny Hostin’s claim he used racist language: ‘I didn’t use the word. Let’s be very clear.’

• Following recent abortion bills, Samantha Bee gives male politicians a lesson in sex ed

Tell us what you think! Hit us up on Twitter, Facebook, or Instagram, or leave your comments below. And check out our host, Kylie Mar, on Twitter, Facebook, or Instagram.

Want daily pop culture news delivered to your inbox? Sign up here for Yahoo Entertainment & Lifestyle's newsletter.