The Big Bang Theory fans spot major nod to sitcom from Kaley Cuoco in Harley Quinn

THE Big Bang Theory fans have spotted a major nod to the sitcom from Kaley Cuoco in Harley Quinn.

The 34-year-old played Penny in the hit CBS show, which came to an end in May last year after 12 seasons.

Kaley now voices anti-hero Harley in the animated series, and in a season two episode, Big Bang fans think they spotted an Easter Egg.

The scene in question sees Harley interrupt a meeting between Batman and Commissioner Gordon on the roof of a derelict building.

As she bursts in, she says: "What is the point in having an elevator if it doesn't work?"

As any Big Bang fan will know, the sitcom had a running joke throughout the 12 seasons about the characters' apartment elevator being constantly broken.

It was only fixed in the season 12 finale, when Penny was shown using it.

Taking their theory one step further, a fan wrote on Reddit that Batman and Commissioner Gordon were also wearing similar colours to those of Penny's friends, Sheldon and Leonard.

They wrote: "The other two are also wearing the same color shirt as Sheldon and Leonard.. sort of."

Meanwhile, last month Harley Quinn boss Patrick Schumacker revealed how Kaley was perfect for the titular role in the animated series.

He told Radio Times: "Most of [the meeting] was just how excited Kaley was at the opportunity to do this departure from The Big Bang Theory, where she was this very nice mid-western girl, to be this supervillain and to do this kind of comedy by way of Quentin Tarantino, in terms of the violence at least.

"It was clear that she would be able to capture Harley's manic quality… I think Kaley was so on board with going nuts in the recording booth, maybe it was cathartic for her or something."