Kaley Cuoco forced to sing The Big Bang Theory theme as Jimmy Fallon puts her on the spot

31-year-old actress appeared on The Tonight Show.

She's the female heartthrob from the hit US sitcom The Big Bang Theory, so many Kaley Cuoco fanatics will be interested in hearing her sing the show's theme tune.

The 31-year-old blonde star was her usual fun, bubbly self when she appeared on last night's (3 May) The Tonight Show starring Jimmy Fallon.

Wowing in a plant print jumpsuit from Natori's Fall 2017 line, Cuoco was asked by a member of the audience if she was familiar with the lyrics to the long-running show's theme tune, which is by Barenaked Ladies.

Thankfully, since Cuoco has starred in the show since its first season back in 2007, she was more than well-acquainted with the song and was more than happy to sing it too. She had us all in doubt when she coyly said: "I can try" when asked to sing it, however.

Which brings us to some background about the track, The Big Bang Theory creators Chuck Lorre and Bill Prady asked Ed Robertson of Barenaked Ladies to come up with a song that would serve as a "sort of history of everything...in about 32 seconds." Not too much to ask, then.

And Cuoco and the famous cast including Jim Parsons will now have plenty of opportunities to sing it since CBS has renewed the show for another two seasons.

In the show, Cuoco plays Penny, who is a struggling actress and neighbour to the scientists Leonard and Sheldon. She loves wine and has a hilarious awkward friendship with Sheldon, fuelled by the fact that they are almost polar opposites in regards to intellect and social aptitude.

Viewers saw a change in Penny's life during season eight when she gave up her acting career for a job as a salesperson at Bernadette's pharmaceutical company.