Fans of The Big Bang Theory already know Kaley Cuoco's Penny is the key to the show's success, but they might not know she's why the show exists at all.

The Big Bang Theory star Kaley Cuoco has reunited with Jim Parsons at his new project. Cuoco, who played Penny on the long-running sitcom, shared a photo with Sheldon actor Parsons after a performance of his new Broadway show,

No Bazinga! — just pure feels. Kaley Cuoco pulled a stealth move, surprising her Big Bang Theory bestie Jim Parsons backstage at his Broadway show, Our Town. Sharing the love on an Instagram story, she hyped his performance: “Go see Jim Parsons in @ourtownbroadway! It is beyond! I surprised him.”

Not every character on "The Big Bang Theory" gets a particularly great ending when the show comes to a close in its 12th season. Sure, Sheldon Cooper and his wife Amy Farrah Fowler (played by Jim Parsons and Mayim Bialik) win a joint Nobel Prize for their work in super asymmetry,

Cuoco, whose recent TV work includes crime series The Flight Attendant and Based on a True Story, had a strange encounter with a stranger in her hotel. To make matters worse, she was "butt naked" when she realised a man, who she thought worked at the hotel, was in her room.

Big Bang Theory' alum Kaley Cuoco gave a sweet update about her daughter Matilda while promoting her show 'Based on a True Story' season 2.

The Big Bang Theory is over but several members of the original cast have found ways to make cameos on other shows in the franchise — including Young Sheldon and Georgie and Mandy's First Marriage. The hit sitcom,

During a fraught moment during The Big Bang Theory, Kunal Nayyar, who played Raj, reached out to another prominent sitcom star for guidance.