15. The original, rejected pilot for the show featured entirely different characters

Unusually, when Chuck Lorre was shopping The Big Bang Theory around between 2006 and 2007, he produced not one but two pilots.

The original pilot, produced in 2006, featured the familiar characters of Leonard and Sheldon, as played by Johnny Galecki and Jim Parsons, but otherwise had an entirely different set of characters.

These included two female leads: “tough-as-nails” Katie along with Leonard and Sheldon’s fellow scientist Gilda, respectively played by Amanda Walsh and Iris Bahr.

This pilot was rejected after poor test audience results, but Lorre was given a second chance: he retooled his next pilot by retaining Galecki and Parsons and introducing Penny, Howard and Raj actors Kaley Cuoco, Simon Helberg and Kunal Nayyar.

14. Jim Parsons originally thought he was auditioning for a game show

Though he was responsible for some of the biggest sitcoms of the day – Two and a Half Men, Dharma & Greg – Jim Parsons had never heard of Big Bang creator Chuck Lorre back in 2006.

This is why, when he was offered the Big Bang pilot, Parsons felt so underwhelmed – he confused Chuck Lorre with game show host Chuck Woolery.

In 2014, Parsons told  “I thought, why are they so excited about it? We should see what the man has to offer before we’re like, ‘It’s a new Chuck Woolery pilot!'”

13. Wil Wheaton got his role through Twitter

Best known to a certain generation as the young , Big Bang might be the project actor Wil Wheaton is best known for these days.

And to think, the role he plays on the show – a sinister version of himself – only came about as a result of a throwaway comment on Twitter.

In 2014, Wheaton told Larry King he “was talking on Twitter about how much I loved the show” when both executive producer Steven Molaro and Big Bang co-creator Bill Prady got in touch offering a part.

Wheaton has since become one of the show’s semi-regulars.

12. Nobody knows Penny’s last name

It’s been 11-and-a-half seasons and, as yet, still nobody knows Penny’s last name (at least, the one she had before she married Leonard).

It’s possible the mystery will be solved in the currently-airing final season, but don’t hold your breath.

In 2014, Steven Molaro told Vulture: “We’re kind of a superstitious lot here. We’ve made it this far without knowing Penny’s last name. I think we’re good not finding out.”

11. A Belarus TV network copied Big Bang without permission

At the end of the season 3 episode The Large Hadron Collision, Chuck Lorre included one of his trademark vanity cards – though this one was slightly different.

Vanity card #277 detailed a case of plagiarism: a Belarus TV network had created a Belorussian carbon copy of Big Bang – complete with characters named Sheldon, Leo, Hovard, Raj and Natasha – called The Theorists.

According to the card, no legal action could be taken as “it’s next to impossible to sue for copyright infringement in Belarus because the TV production company that is ripping us off is owned and operated by the government of Belarus.”

The Theorists was soon cancelled regardless.

10. Numbers in the show carry secret meanings

Big Bang is awash with in-jokes, none-more-so than where recurring numbers are concerned.

In the show, Sheldon’s favourite number – which appears on his clothing from time to time – is 73. This is in reference to the year Jim Parsons was born, 1973.

Apartment numbers also carry a hidden meaning: Amy Farrah Fowler’s, 314, is the first three digits of pi, while Wil Wheaton’s, 1701, refers to then hull number of the USS Enterprise, from the .

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9. Mayim Bialik really has a PhD in neuroscience

Mayim Bialik might not be much like her Big Bang character in real life, but the two do share one thing: they both have a PhD in neuroscience.

In fact, Amy Farrah Fowler was rewritten as a neuroscientist because of Bialik’s casting, with Bialik telling Variety in 2015 that producers “didn’t have a profession for my character when I came on in the finale of season 3.”

According to Bialik, “Bill Prady said they’d make her what I am so I could fix things (in the script) if they were wrong.”

8. The cast are the highest paid TV actors in the world

Unsurprisingly, considering the show’s success and how much said success is down to its cast, The Big Bang Theory’s stars are paid handsomely for their work.

Since 2017, Johnny Galecki, Jim Parsons, Simon Helberg, Kunal Nayyar and Kaley Cuoco have been making $1 million per episode.

Considering each season consists of 24 episodes, it should come as no surprise that the Big Bang principal cast members are as a result the highest paid TV actors in the world.

7. Animals have been named after the show

Not that you couldn’t already guess from the show’s many science-based cameos, but The Big Bang Theory is just as popular with scientists as is is with general audiences.

This is evidenced by the  have been named for the show, specifically after Sheldon’s favourite catchphrase.

The two creatures are the Bazinga rieki, a small jellyfish; and the Euglossa bazinga, a Brazilian orchid bee.

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6. It’s the most successful sitcom since Friends

Though Big Bang peaked in season 9 with an average of more than 20 million viewers, the show still rakes in huge figures for a modern TV show.

Since 2012, the show has never dropped below an 18 million viewers per season average; for the past four seasons, it’s been the most-watched comedy on television.

This makes Big Bang the most successful sitcom since Friends, which never once dropped below a 20 million per season average.

5. Kaley Cuoco and Johnny Galecki dated in real life (secretly)

After a number of seasons of will-they-won’t-they romance, Leonard and Penny finally tied the knot in season 9.

In real life, however, Leonard and Penny actors Johnny Galecki and Kaley Cuoco didn’t work out so well as a couple.

From 2007 to 2009, Galecki and Cuoco dated for real, though fans of the show didn’t find out until Cuoco admitted to it in an interview in 2010.

4. Soft Kitty is a real song

Soft Kitty, Sheldon’s favourite comfort song, isn’t a Big Bang invention, but has its origins in a folk song that dates back centuries.

The show’s co-creator Bill Prady first heard the song from his daughter, who sang it at pre-school, though her teacher had first heard it while working in Australia.

This was the children’s song Warm Kitty, with words written by Edith Newlin in 1937, and itself based on an 18th century Polish lullaby called Wlazł kotek na płotek.

3. Kate Micucci could have played Amy

In season 6 – and, later, as a guest star, season 10 – Kate Micucci played Raj’s would-be girlfriend Lucy.

This wasn’t the first part on the show that the Garfunkel and Oates comedian had auditioned for, however.

Before she played Lucy, Micucci was in the running to play Amy Farrah Fowler, though Mayim Bialik just beat her to it.

2. The cast learned to play instruments just for the show

The theremin might notoriously be one of the most difficult instruments to play, but Jim Parsons is one of the relatively few to have it mastered.

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Parsons didn’t know how to play the electronic instrument before he joined The Big Bang Theory – he learned it specifically for the show.

Parsons wasn’t the only one: once it was decided that Amy Farrah Fowler would play the harp, Mayim Bialik set about learning the instrument from scratch.

1. The show was originally called Lenny, Penny and Kenny

Before Chuck Lorre and Bill Prady finally decided on The Big Bang Theory for their science-based sitcom, they considered a different title.

The working title of the show at first was the perhaps less suitable Lenny, Penny and Kenny.

That’s right: while Penny and Leonard kept their names, Sheldon in this version of the show was named Kenny.