'Big Bang Theory' Series Finale: Breaking Down the Biggest Plot Twists With Inside Secrets! (Exclusive)

Sheldon would recommend a hot beverage to cheer you up -- but we're going to spill the behind-the-scenes tea instead!

They went out with the biggest bang possible.

After a special one-hour series finale, The Big Bang Theory is officially over. We know you're sad. (We are too!)

Normally, Sheldon would recommend we get you a hot beverage to cheer you up -- but instead, we're going to spill the behind-the-scenes tea on all the biggest plot twists!

ET called up Big Bang's executive producers Steve Molaro and Steve Holland to get their exclusive explanations about the two-part finale's sweetest, smartest and most shocking moments!

"We just did our best to end the series in a way that honored these characters that we've loved for 12 years," Molaro dished over the phone last week.

"We wanted to make sure that everyone kind of had their moment to shine in the finale," Holland added.

From Penny and Leonard's newest addition, to Sheldon's monumental moment of growth, and Raj's famous new friend -- keep reading for all the inside details about how these moments happened!

The Elevator Is Fixed


For 12 long seasons, Penny, Leonard, Sheldon and the rest of our geeky gang was forced to walk up and down three flights of stairs any time they wanted to enter or exit their Pasadena apartments. But all of that was finally fixed with one surprising "ding!" and a delighted Penny stepping out of the doors.

The Big Bang showrunners revealed that the question they've most received from fans over the past 12 seasons was centered around that infamous broken elevator. "Originally, when we were talking about the finale, [the elevator reveal] was going to come much later," Holland dished. "And then story-wise, it felt like the perfect moment and it felt like a much bigger surprise coming so early in 23 instead of at the end of 24."

Leonard and Penny Are Pregnant


After years of will-they-won't-they, Leonard and Penny are having a baby! After a night of drinking at the Cheesecake Factory with Sheldon in the first part of the finale, Penny came back and "attacked" Leonard. In the next episode, which took place two months later, fans discovered that Penny and Leonard are very excited about their upcoming addition -- even if they can't agree on the story of how it happened.

"Attacked you?" Penny scoffed with a smile when Leonard recalled their special night together. "I said, 'Do you wanna?'"  

"And I was helpless," Leonard replied sweetly to his wife.

Turns out, this surprising pregnancy has been part of the plan since Leonard once boasted that their babies would be "smart and beautiful" way back in the pilot episode.

"I think we always liked the thought honoring and going back to the fact that Leonard and Penny were the beginning of this show and our central relationship," Holland revealed. "It just felt like really nice closure to them and I think writing against it this season it helped make it a surprise at the end."

Sheldon and Amy Win a Nobel Prize


Ladies and gentlemen, Sheldon Cooper and Amy Farrah Fowler-Cooper have won a Nobel Prize. (And no, this is not a Bazinga!) Not only did they win one of the world's biggest honors, Sheldon Cooper also did the unthinkable: he turned his acceptance speech into a tear-jerking appreciation speech for all of his friends. 

The executive producers confessed that Sheldon's big moment of empathy is "one of the few pieces" they've always known would happen in the finale. 

We knew that they would win and he would give his speech, but instead of making it about himself, he would make it about all the people that got him there. That was something we were talking about months ago," Molaro said.

Holland stressed that although Sheldon can be "self-centered," it was important for them to show that this brilliant man is still evolving as a friend. "[It's] just the biggest growth that this character can have in this moment that he's wanted his whole life," Holland said. "Instead of taking that spotlight on himself, he took that moment and he made it about his friends. And that just seemed like the biggest sort of character growth we could give him in the end."

Sheldon ended his speech by saying, "In my own way, I love you all," and Molaro revealed that this was the perfect way for this "complicated" character to express his feelings.

"I think the finale shows that these people are really patient with him. I think the way he shows love is not always typical or obvious and coming right out and saying it is about as close as we’ve seen him come to really letting his loved ones feel that love," Molaro concluded.

Holland added that is also "just felt right" for the return of Amy's tiara. "It was such a big moment for her character when she got the tiara," he recalled with a laugh. "She wore it at her wedding and so it just felt right that she would have it on at the Nobel Prize ceremony."

We Meet Howard and Bernadette's Kids


For more than three seasons, Big Bang fans had only heard of Howard and Bernadette's two children, Hallie and Michael, -- until now. For the very first time, the entire Wolowtiz family appeared together on-screen in the finale. Despite the sweet surprise, the showrunners revealed that seeing Howard and Bernadette's kids were never part of the plan -- not even for the final episode! 

"That wasn’t even planned when we were going in to write the scene. We were in it and then [Big Bang creator] Chuck [Lorre] said, “Why don't we just show the kids? It’s the last episode and we never have to show them again, so why don't we show the kids?," Holland explained.  "Part of the reason to not show them was it let us get away with not having to have kids on the set, which is difficult."

"And I will tell you that based on shooting that one scene, we were right," Molaro added with a laugh. "But that scene did turn out very cute!" It sure did. 

Raj's Self-Love Happy Ending


In a delightful twist, Raj Koothrappali ended up taking actress Sarah Michelle Gellar to Sheldon and Amy's Nobel Prize ceremony. (For the full story on how this surprise guest role came to be, check out our full exclusive article here!)

Sarah, who's married in real-life to actor Freddie Prinze Jr., stressed that this "wasn't a date," but Raj was still delighted to bring the Buffy the Vampire Slayer star as his platonic plus one.

Raj has come a long way since the Big Bang first premiered -- remember when he couldn't speak to women?! -- but the showrunners felt that it was important for this character to still be single. "To us that felt like a more satisfying end," Holland said. 

"I think the Kooth and Anu storyline was really nice and good for Kooth and got him some growth, but it didn't feel right for us to have him go off and enter into this relationship," Holland said, referring to Raj and Anu's breakup in the penultimate episode. "Not everyone has to end up married. Not everyone has to end up in a relationship. I still think there’s hope for Koothrappali and still think he, ultimately, finds someone who’s amazing and perfect for him. But I think it was a way for him to have a satisfying end to that story, but not tie everyone up in a relationship bow by the end."

Did You Catch This Easter Egg?


In addition to big plot twist, the Big Bang showrunners also made sure to include a few small Easter eggs for the fans -- and our favorite was in the beginning of the very last episode, "The Stockholm Syndrome."

"Leonard and Sheldon are glueing the DNA statue back together and Leonard says, 'This may be the glue talking but that was the most pleasurable 139 and a half hours,'" Molaro explained. "Well, we figured out that is how many hours of Big Bang Theory that have been created over the last 12 years."

"279 total episodes, which is 139 and a half hours," he added. 

The Big Secret About The Final Scene


For the friends, family, fans and press members who were lucky enough to score an invite to The Big Bang Theory’s final live audience taping, they thought they were getting to see the entire episode. They thought wrong.

The showrunners dished to ET that they pulled one last “Bazinga!” and the final scene with Leonard, Sheldon, Penny and the rest of the geektastic gang eating chinese food in the living room was kept secret until the episode aired.

"It's how we wanted it to end," Holland spilled. "We knew the show and the final episode was going to involve some travel, but we really wanted to end it in our home."

The showrunners said they "talked about it a lot" and realized that they had a very specific ending in mind: an ending that didn't feel like an ending. 

"This show brings so much happiness to people and as a fan of it, I wanted to know that tomorrow morning they were still going to be hanging out together," Molaro explained. "So we kind of summed it up that this show can say goodbye, but the characters don't need to."

"Their lives are continuing and going on. It wasn't an ending for them," Holland added. "They’re still going to get up the next morning and go to work and Leonard is still probably going to have to drive Sheldon and they're probably going to play car games. For them, their lives are going to go on, but we’re just not going to see those stories any more."