The Big Bang Theory ended its 12 season run in 2019, but millions still watch every day thanks to syndication and streaming. Fans can't get enough of Leonard, Sheldon, Penny, Howard, Raj, Amy and Bernadette. This group of friends were often found sitting around Sheldon and Leonard's coffee table, eating take-out. They loved each other, but who would think that this mismatched crew belonged together?

Sheldon, Leonard, Raj and Howard were genius science-nerds. Penny was an ex-homecoming queen and wanna-be actress from Nebraska who had nothing in common with the guys across the hall. Bernadette was also quite intelligent, but let's be honest, what did she see in Howard? Amy was so socially awkward when she first met the group, and later became obsessed with Penny. And Sheldon pretty much annoyed them all.

In real-life, the actors were different from their characters. And so were their relationships.

9 Jim Parsons And Simon Helberg Were Close

Jim Parsons, Kunal Nayyar, and Simon Helberg at a charity benefit
Via: Deposit Photos

Their characters didn't get along very well, but Jim Parsons and Simon Helberg were close during the entire run of The Big Bang Theory, and are still friends today.

When the series was coming to an end, Parsons said, “I’ll particularly miss Simon Helberg; we spend a lot of time together, we go back and forth to our dressing rooms, we’ve talked for almost 12 years now.”

Maybe that was part of what made Jim tear up when Sheldon thanked Howard and referred to him as "Astronaut Wolowitz" during the finale.

8 Did Mayim Bialik And Johnny Galecki Kiss?

Johnny Galecki and Mayim Bialik
The Things

Mayim Bialik and Johnny Galecki were friends long before Mayim joined The Big Bang Theory. They had both been acting since their early teens. In the early 90s, Bialik played the title role in the NBC series, Blossom. In an episode titled, "Sex, Lies and Teenagers", Blossom has her first kiss. The boy who kissed her was none other than Johnny Galecki. They remained friends after that, Mayim even invited Johnny to her "Sweet 16".

Years later, on an episode of Conan, the two were asked to recreate their first kiss, and they were happy to do so.

Related: The Barenaked Ladies Were Moments Away From Cancelling Their Iconic Theme Song On The Big Bang Theory

7 There Was Mutual Admiration Between Kaley Cuoco And Jim Parsons

Kaley Cuoco and Jim Parsons
Via: Instagram

It is well known that because Jim Parsons did not want to continue on as Sheldon, The Big Bang Theory came to an end. Kaley Cuoco has been honest in saying that she would have liked to continue on as Penny. But she has no animosity at all for Parsons. She said in a 2021 Variety article, “Jim was 100% the breakout, deservedly — the stuff he did on that show was an out-of-body experience."

The two had a genuine friendship on the set, and that has continued. They spend time together and never forget each other's birthdays. Jim was especially supportive when Kaley was nominated for a Golden Globe for The Flight Attendant, and when she didn't win.

Related: Kaley Cuoco Character Guide: Every Top Role The 'BBT' Star Has Taken On

6 Were Kunal Nayyar And Simon Helberg As Close As Their Characters?

Simon Helberg and Kunal Nayaar
via: Instagram

Raj and Howard were super close, sometimes almost oddly close. It turns out that Simon and Kunal were also good friends. Towards the end of the final season of Big Bang, Kunal posted a picture of the two, with the caption, "12 years, with my brother from another. I swear he loves me, I think."

The friends often post about each other, and are very supportive of each other's projects.

Related: Jim Parsons Was Genuinely 'Stunned And Confused' When He Saw Sarah Michelle Gellar During His Emotional Big Bang Theory Speech

5 A Mayim Bialik And Simon Helberg Reunion

The Big Bang Theory's cast at the People's Choice Awards
Via: Instar

Mayim is so fond of Simon that she wrote a script with him in mind. Bialik wrote and directed, As They Made Us, which is about a woman, Abigail (Dianna Agron), who deals with the slow death of her father (Dustin Hoffman). Helberg plays Abigail's estranged brother. It is based on Mayim's own experience.

Mayim said about casting her friend, "It was very, very special to work with Simon; I basically wrote with him in mind, but I never thought he would do this movie. It also was very important to have someone who knew me when my father passed away, who knew my family, and it felt like having a friend there."

4 Do Mayim Bialik And Kaley Cuoco Hate Each Other?

Mayim Bialik and Kaley Cuoco friends
via: NBC

During the show, there were constant rumors about beef between Mayim and Kaley. It was said that there fighting got so bad that they once needed to be separated from each other.

It looks like these rumors were not actually true, and that the two are close. When asked if she and Cuoco were friends, Bialik told Wired, "Well, we worked together for nine years and I went to her wedding and celebrated things with her. I would say we're friends."

Since then, they both have posted tributes to each other on social media.

3 Jim Parsons And Johnny Galecki Did Not Like Each Other At First

Johnny Galecki and Jim Parsons
via IMDb

The friendship between Sheldon and Leonard was one of the sweetest things on The Big Bang Theory.

But when Galecki first met Parsons, he asked his new costar to run lines with him, and Parsons said no, “We were outside in the hall beforehand and I asked if he wanted to read the scene through a few times first,” Galecki told The Hollywood Reporter. “He said no, and I said me neither. We just chatted.”

After that first encounter, the two developed a great friendship. They bonded playing Sheldon and Leonard. Unfortunately, they had something else in common. They both lost their fathers in tragic car accidents. This may have also brought them closer.

Related: Simon Helberg Had A Selfish Reason He Was Happy About The Big Bang Theory Coming To An End

2 Jim Parsons And Mayim Bialik's Friendship Led Them To Work Together Again

Mayim Bialik and Jim Parsons
via news.yahoo.com

Bialik and Parsons loved working together and had a special friendship. Mayim spoke to People about their emotions scenes, such as Amy and Sheldon's wedding, "Although it's sometimes hard to keep a straight face saying such lovey-dovey things, there's no one I would rather say them to than Jim."

After Big Bang ended, the duo worked on Call Me Kat together. Bialik played the starring role, while Parsons was an executive producer. Mayim spoke to Us Weekly's, Watch With Us podcast about getting the role, "When Jim brought it to me, I thought he was just asking my opinion because we were friends and we have a lot of similar tastes. I was like, 'That sounds great. I totally think that's a great idea!' He was like, 'No, Mayim. I'm telling you about this because I want you to play her.' So I was totally shocked."

Their friendship is going strong.

1 Kaley Cuoco And Johnny Galecki Got Over Their Break-Up

Johnny Galecki, Kaley Cuoco and Jim Parsons
Instar

Most Big Bang fans know that Kaley and Johnny dated. They met on the set, and Kaley admits to having a crush on her costar. They began dating, but kept it quiet for a while. Cuoco said, "He was very protective of what the fans would think, because we wanted them to want Leonard and Penny together so badly, that if they saw us together in real life, it could ruin the fantasy."

After two years, the couple ended their relationship. Cuoco said of their breakup, "...we were together for a long time. We really adored each other, and we were lucky because as our breakup was happening, there was no foul play, there was nothing bad about our relationship ... it just ended."

Luckily, the two were able to go back to being friends. Since then, there has been on and off speculation about them getting back together, but it was not true. The two remain very close. Galecki recently told Vanity Fair, "I adore the friends that we are. I think I might value my relationship with her more than any other previous relationship or relationship afterwards. We just have such a bond that I appreciate so much. And I think that's part of our great friendship."