The first instalment also introduced Penny (Kaley Cuoco) who quickly became a huge part of their lives when she was introduced as their next-door neighbour.
These relationships blossomed and evolved throughout the 12 seasons, and even saw Leonard and Penny get married.
While the show sort of brought all of the stories to an end, there wasn’t a by-the-numbers conclusion that viewers of other sitcoms have come to expect
In a poll recently run by Metro.co.uk, the most desired characters to return for a spin-off are Leonard and Penny – who have always been the crux of the show.
The couple have maintained a comedic chalk-and-cheese relationship, with Leonard struggling to maintain his composure around Penny, while Penny found speaking to Leonard difficult through all of his scientific jargon.
Penny and Leonard won 40 per cent of the vote, leaving them the clear leaders in popularity from the show’s viewers.
Right behind them was Raj (Kunal Nayyar), who did not really receive a happy ending, and was left single by the final episode, still looking for love.
Following Raj’s silver medal, Sheldon and his wife Amy (Mayim Bialik) placed third, which is a little surprising.
Considering Young Sheldon is still going strong and has a third season on its way, it would make sense for viewers to want to see a lot more of Sheldon now he has settled down.
Die-hard fans of the show can rejoice, as Penny star Kaley seems open to rejoining the show, as revealed in an interview with Entertainment Tonight back in the summer.
She explained: “I mean, it’s 12 years of my life, we’ve all had a lot of ups and downs in the last 12 years we’re a very close group and, you know, we have a legacy of the show.
“It’s something I’ll have for the rest of my life. It’s something I’ll probably compare every project to, like nothing will be like Big Bang. It just is what it is.
“It’s made me who I am. It’s given me so many great things and blessings and I’ll be very indebted to the show and Chuck Lorre forever. I would be interested in working with Chuck again, and these are Chuck’s characters and it’s really whatever he would want.”
Unfortunately, Leonard star Johnny doesn’t feel the same way.
The show was rumoured to be coming to an end because Sheldon star Jim didn’t want to continue with the show – and this is a huge part of why Johnny wouldn’t return.
Speaking to News.com.au, he said: “Absolutely not. The show could not continue without Jim.”
To make matters worse, Kaley recently told People she hadn’t spoken to the rest of the cast since the show finished.
“You know what, I haven’t really talked to anyone,” she confessed.
“This feels like a summer hiatus for us, so we all go off in our own directions.
“I think it’s going to hit us all more in September, when we would normally [go back to the show].”
The Big Bang Theory season 12 is available on CBS and All4.