In early October 2022, Jessica Radloff released a The Big Bang Theory tell-all which featured behind-the-scenes facts and interviews about one of the most well-received TV shows of all time. Titled The Big Bang Theory: The Definitive, Inside Story of the Epic Hit Series, the book is already a bestseller and creating buzz over the show since it ended in 2019.

With over 500 pages of fascinating tidbits, fans are loving the inside scoop. But with so many interviews and things to know about the cast and characters, some stories got lost in the fray. At the same time, there were huge reveals that shed new light on the series.

Kaley Cuoco Cried The Most When She Learned Season 12 Would Be The Last Season

Penny tells Leonard she's pregnant in TBBT

Fans thought they knew everything about TBBT, but one of the more sought-after pieces of information from the book was how the show came to a close. As shared by TV Line, Jim Parsons (Sheldon Cooper) was ready for a new beginning after season 12 and met with executive producers Chuck Lorre and Steve Molaro to discuss his departure from the show.

RELATED: Everything Fans Know So Far About The Big Bang Theory Official Book

The producers were shocked but knew the show couldn't continue without the one and only Sheldon Cooper. Things got even more emotional when Parsons told his cast members. Cuoco said in the book, "We cried for hours… We thought we were going to do another year, so all of a sudden your life kind of flashes before your eyes. I looked at Chuck [Lorre] and said, ‘What are we going to do?’ I couldn’t breathe. It just felt like a death.”

...But Things Were Awkward Among The Cast After Jim Parsons' Departure

Penny hugs Sheldon in TBBT

One thing to know about Jim Parsons and Kaley Cuoco's friendship is that they became so close during filming that his departure from the series made things hard for Cuoco and the cast.

TV Line noted that Molaro felt the cast was "icy" after Parsons' admission. “Kaley could barely make eye contact with Jim during the runthrough, but they got through it," he said. After a few days of reflection, the cast was back at work and ready for a fresh start after a few awkward meetings and conversations. In the end, the cast felt blindsided by Parsons' departure and wished it was treated differently.

Kevin Sussman Was Originally Howard Wolowitz

Stuart and Howard talking in the kitchen over dinner on TBBT

Kevin Sussman's Stuart Bloom had some of the funniest quotes throughout TBBT, but that almost didn't happen. ET Online mentioned that Sussman was originally supposed to portray Howard Wolowitz. However, after a week, things changed and Sussman transitioned from Howard to Stuart.

RELATED: Stuart Bloom's 10 Funniest Quotes On The Big Bang Theory

Radloff wrote, "When I talked to Kevin Sussman, Kevin told me that he actually had the role of Wolowitz first. My jaw was on the floor. I wanted to know why have you never said anything?'" Radloff praised Sussman's silence, saying, "[Sussman] never wanted to get in Simon's head and to make him think [he wasn't] the first person cast, which was so incredible to do that."

Marisa Tomei Could Have Been Penny

Marisa Tomei Spider-Man Aunt May

Marisa Tomei is most known for her roles in the Spider-Man franchise, My Cousin Vinny, and The Big Short among others. And thanks to the tell-all, she almost landed the role of Penny on TBBT.

After landing the role of Sheldon, Parsons read a few lines with Tomei to see their chemistry. If Tomei was chosen for the part instead of Cuoco, Parsons admitted "What a different world that would have been." — not just for the show but for Penny's character.

A Horse Riding Incident Brought Kaley Cuoco & Chuck Lorre Closer

Penny bartending and talking to Sheldon.

There were some amazing TBBT scenes at the Cheesecake Factory since it was where Penny worked and the men ate weekly. Penny took up bartending briefly when viewers saw her behind the bar. In reality, Penny had to be behind the bar because Cuoco injured her leg.

However, the book explained (via ET Online) just how serious the accident was. After being hospitalized, doctors told Cuoco that there was a possibility they'd have to amputate her leg. Radloff noted the role Lorre played in her recovery, "Chuck helped get her the care at Cedars-Sinai that she needed and... when she was in recovery, he would come and play his guitar for her." The ordeal brought Lorre and Cuoco closer. "She became like family, it wasn’t just a business relationship," Lorre said.

Johnny Galecki & Jim Parsons Had "Accelerated Bonding"

Leonard and Sheldon arguing over a sweater on The Big Bang Theory

Radloff explained that Galecki and Parsons were the two first cast on TBBT since the series would focus on their friendship. Knowing how close they were supposed to be on-screen, Galecki invited Parsons over for "accelerated bonding."

With the intention of spending a lot of time together before filming, the pair spent six-straight hours together. The Hollywood Reporter quoted Galecki, "We had many bottles of wine and learned we had so many things in common..." After a few glasses of wine, deep conversations, and a lot of sleep, Galecki and Parsons became instantly close.

The Invention & Importance Of Amy Farrah Fowler

Amy and Sheldon at the movies in The Big Bang Theory

Amy and Sheldon's relationship on TBBT became the face of memes and countless theories. But how did Amy's character come to be?

Entertainment Weekly shared Mayim Bialik's Amy Farrah Fowler was only supposed to be in one episode. Once Parsons worked with Bialik, he said "I remember saying to Todd, 'I will not let this character go without a fight.'" Bialik was later offered a full-time role and the actress's character evolved into her own person.

Kunal Nayyar Was Dropped Behind Chuck Lorre's Back

Raj sitting at his desk sulking on TBBT

Raj was the ultimate third wheel throughout TBBT. He loved his friend group and longed for a romantic partner but it never happened for him by the time the series ended.

RELATED: 8 Hilarious Times Raj Was The Third Wheel On The Big Bang Theory

Kunal Nayyar starred as Raj Koothrappali and made him both lovable and brilliant. In a strange twist of fate, Nayyar almost didn't keep the role after he was given it. Starte Facts explained that Lorre found out Nayyar wasn't at a few meetings while he was out of town, and it was all because a CBS executive wanted to recast him. Lorre said, "I called the execs at CBS and said, 'You can't fire him. I cast him, I believe in him, I'll take responsibility for this decision. He's my guy. If I'm going to fail, I'm going to fail on my own choices. I'm not going to fail on someone else's choices.'" And as fans know, it paid off.

Melissa Rauch's Most Embarrassing Moment On Set

Bernadette and Sheldon playing a game on TBBT

Like Bialik, Melissa Rauch (Bernadette Rostenkowski-Wolowitz) joined as a series regular around the same time. As a newbie on set, Rauch was nervous and wanted to make a good impression on her castmates.

Looper shared a moment in the book, however, that haunted Rauch. On her first week, she accidentally threw out the slip she needed for meals. Unsure of who to ask for a replacement, Rauch went through her garbage to find it. While digging, an entertained Galecki saw her and said, "You alright there? Just picking through our garbage?" Rauch was humiliated but Galecki praised his bond with Rauch after that moment

Why Did Kaley Cuoco Cut Her Hair Anyway?

Penny and Sheldon Cooper in The Big Bang Theory

In season 8, Penny debuted a much shorter haircut that shocked viewers. And thanks to the tell-all (via Yahoo), her change of hair surprised her castmates and producers as well.

Cuoco said, "I just f***ing cut my hair off and didn’t tell anyone. I did it for an independent film called Burning Bodhi, and basically showed up to our Big Bang wrap party with short hair." Many felt the haircut was a cringey Penny moment, and it's an action she regrets today because it ended up taking more time in the hair and makeup chair just to style it for the scene.

NEXT: Penny's 10 Cringiest Parts On The Big Bang Theory (According To Reddit)