Johnny Galecki admitted that from the start even before the show aired, the cast of had the perfect chemistry during the table read. It felt as though they had been together for years.

Introducing other characters was a major risk, especially and Melissa Rauch's involvement. As Bill Prady revealed, there was never a set plan in place and in fact, Amy's character seemed to be short-term more than anything else.

We're going to reveal a major driving force behind the scenes to Bialik sticking around for the long-term. We'll also reveal what the approach was in the writers' room to putting the show together.

Mayim Bialik's Inclusion On The Big Bang Theory Was Initially An Episode By Episode Deal

At start of her journey on , . Creator Bill Prady revealed after the audience reacted positively to Amy, they continued to bring her back on an episode by episode basis, all depending on the way the audience would react.

“All right, well, let’s have her come back one more time, and see what happens.” And you go, “Oh, that went well.” And there have also been people where we say, Oh, that didn’t go well.

Those people, they don’t belong together, for whatever reason. So there was never a plan," Prady reveals.

As for Bialik, she admits that given that it didn't provide any guarantees.

She tells EW, "They decided after that summer break that I would be brought back, but they book you one episode at a time, which is not stressful at all! After my episode in the season three finale, I literally thought my character might never come back. I had been out of the industry for so long . . . it really could have gone either way."

Although both Bialik and Melissa Rauch thrived on the series, they were not part of the plan early on.

Mayim Bialik And Melissa Rauch's Introductions Were Not Planned Given That The Show Creators And Writers Didn't Look Too Far Ahead

Were the character of Amy and Bernadette planned in advance? The answer is no. According to creator Bill Prady, Chuck Lorre took the approach of writing the script day by day, and organically. This meant that the series never looked too far ahead, and that held true for the long-term involvement of Any and Bernadette.

Prady reveals, "Chuck had always insisted on not doing that, on not arcing stories, on not planning ahead.

And so every question about, “Did you plan when you added, when you thought to add,” all of that, the answer is no. Everything from adding characters, which was never planned, it was just, well, it would be logical that we would see that person again.

"The characters added themselves by virtue of what the other characters thought of them. So there was never a master plan, there was never a design, there was never a decision to approach a particular demographic. It was always the natural evolution."

The two stars turned out to be a perfect fit on the show. Jim Parsons was a major reason for Bialik in particular sticking around, but there was another major supporter of the actress behind the scenes.

Chuck Lorre Insisted Mayim Bialik Kept Coming Back To The Big Bang Theory Even Though Her Character Was A Risky One

Showrunner Steve Molaro revealed other details of Mayim Bialik on the series - and he agreed, there was no real plan in place to keep her around long term. However, there was one constant behind the scenes and that was Chuck Lorre constantly pushing her involvement. Molaro and the writers were unsure at the start given how similar she was to Sheldon, making the character a risky one.

But eventually, it proved to be the perfect add-on.

"Chuck was the biggest early adopter and proponent of Mayim," Steve Molaro reveals with

"Even when we felt that the character may be polarizing—because some viewers weren't comfortable with the idea of Sheldon being involved with a female—Chuck was like, "I don't care, you put that face on TV!" We, in the writers room, were into it, but we didn't know where it was going to go."

"We didn't know they were to have a second date, or how that was going to play out and keep evolving through the years. But we went into it like we do with all additions to the show and all the characters: We're hopeful and trying to do our best to make it grow into something better and interesting; that was one of those that obviously did. But it took a little while to shake off the "female Sheldon" description and let her become her own person."

Mayim herself understood the risk of her character but in time, she was able to make it her own and become a main cast member on the series.