The iconic CBS comedy will come to a close on May 16, and while the cast isn't spilling details on how the series is wrapping up, they've put quite a bit of thought into how they'll say goodbye.
"There's no manual," Johnny Galecki told ET's Nischelle Turner during our 16th set visit over the course of Big Bang's 12 seasons. "It's a very, very unique experience that we've all shared."
"So many people are a part of it too," Kaley Cuoco added. "There's so many different people and families and work-related and our families. It just goes so deep and so many people are connected to this show and so many fans. It's created its own little world."
For Melissa Rauch, it's not the people she'll miss, because she fully intends on remaining friends with all of them. "I know we're all bonded here together for life. It's not so much, 'I'm never going to see these people again,'" she shared. "I think it's about missing the people in these circumstances, like huddling together before we go out for intros or laughing together in between scenes. That's what I'm sad about the most."
Our favorite characters have been through a lot over the course of the show, from weddings to babies to just learning how to talk to the opposite sex.
"When I spoke to Penny for the first time... Well, permanently when my character started talking to women, that was pretty cool," Kunal Nayyar joked. "That was big for me."
"Proposing to Bernadette would be a big one for me. Although he messed it up," Simon Helberg said. "I think, if I remember, he proposed right away, I believe, and she said, 'What are you doing?'"
This video is unavailable because we were unable to load a message from our sponsors.
If you are using ad-blocking software, please disable it and reload the page.
Watch Kaley Cuoco Tour 'The Big Bang Theory' Set in 2007 (Flashback)
"Oh gosh! What defines you in the last 12 years? It's not easy to answer," Cuoco confessed. "That is hard to answer because that's what I loved about the show... The relationships have been natural. It's all felt all realistic, even [Penny and Leonard's] relationship, how it's been on and off at times. It's felt really realistic to me."
The actress -- who had yet to read the final script at the time of ET's set visit -- was hoping the show's last episode would feature a big elevator moment. Nayaar and Helberg, meanwhile, offered their hilarious advice for fans who might not be happy with Big Bang's ending.
"Blame the writers! Really, we have nothing to do [with it]. We just show up and say the lines," Nayaar cracked.
"If it's great, we'll take credit. If it's bad, we will blame the writers," Helberg quipped. "I don't even know what it is yet, so in truth, we will blame or celebrate the writers depending on what they come up with. But [finales] are hard."
"I think only one character dies in the finale, yes?" Nayaar joked.
"We go straight up to heaven [in the elevator]," Helberg added.
The Big Bang Theory's finale airs May 16 at 8 p.m. ET/PT on CBS, and Thursday's episode of ET -- featuring tons of exclusive content -- will be broadcast from the set of the sitcom. See more on the series in the video below.