"It was not talked about at all," executive producer Steve Molaro exclusively dished to ET at PaleyFest earlier this month. "We were writing that Valentine's Day episode and there was no baby in the outline."
"There were four or five of us in the writers' room on a Saturday afternoon and we were at the end and just thinking of ways to finish the episode," the showrunner recalled. "I just said, 'I don't even know why I'm pitching this, but what if Bernadette says to the rabbit, 'I'll find another time to tell him I'm pregnant.'"
"A quiet fell over the room and then several writers were like, 'Oh my god, can we do it please?! That's so amazing!'" Molaro shared. "And I said, 'Screw it, let's do it. Type it! Have her say it.' And that was it."
Bernadette's baby news was even kept under wraps from Big Bang's creator and head honcho, Chuck Lorre, until right before the episode was filmed.
PHOTOS: "Big Bang Theory" cast
"I handed the script over to Chuck the next morning and I said to him, 'I tried a couple things. See what you think,'" Molaro explained. "He had no idea and he came back later with the script and he goes: 'So, Bernadette is pregnant? Sure, why not? Go do it!' and he walked out and that was that."
Although the creators and fans are thrilled at the idea of the new little addition to the series, thecomedy's cast members are understandably hesitant about having infant co-stars.
"It will be interesting if we have fake babies or if we actually will have them around," Kunal Nayyar pondered. "Because then we're going to have to cast babies like the Olsen twins."
When we asked Kaley Cuoco if she's excited to be working with some potential twins on the Big Bang set, the blonde beauty was completely unfiltered with her response: "No, I'm not," she said bluntly.
"Twins? Really?!" she exclaimed after realizing that more than one Big Bang baby could be crawling around the comic book store. "Oh wait, yeah, because they have to get multiples. Oh, god!"
Jim Parsons, on the other hand, is a little bit more optimistic about the plot twist. "Jim is fine with a baby coming on the show because it's not mine," the Emmy winner said with a laugh.
But the bigger question is, how is Sheldon going to feel about having a baby around? "I don't know if he's going to be excited about it, but I kind of hope not because that would mean that I have to hold it for lots of episodes," Parsons said.
Cuoco confessed that she has an idea to postpone the inevitable baby invasion. "Maybe [Bernadette] can be pregnant for, like, three seasons so we can wait a couple of years, but we'll see," she said.
"No dogs and no babies -- that's my rule," Cuoco added. "At home, yeah, but not on set. Not at work."
Not to worry, guys! Molaro assured us that this bundle of joy will not change the dynamic of TV's No. 1 comedy. "The fact that it's Bernadette and Howard is a way that it's manageable," he admitted. "If it was Penny, that could seriously alter the DNA of the show."
"They don't live on the main set," Molaro continued, "and there are baby sitters, and there are parents, and there are grandparents, so I think this is a way to introduce this fun without truly altering what the show is."
The Big Bang Theory airs Thursdays at 8 p.m. ET/PT on CBS.