26 Things You Didn't Know About "Big Bang Theory"

The "Soft Kitty" song Sheldon's mom used sing to comfort her son is a real song. "It's from my daughter's preschool in Sherman Oaks," Prady revealed at PaleyFest. "It was from Australia, and one of the teachers heard it there."

Before Bialik joined the cast, the show referenced her childhood role on Blossom, when Raj suggests they invite actress Mayim Bialik to join their bowling team. Then, in Season 6, when Amy and Sheldon compile a list of potential couples costumes, one is Blossom and Joey. Another was Dharma and Greg, a different show from creator Chuck Lorre.

While Sheldon Cooper is obsessed with Star Trek, Jim Parsons actually has never watched it or Doctor Who, he revealed to Time.

She's the only cast member with an education in neuroscience, and often likes to make sure her scripts are scientifically accurate!

Sheldon Leonard is a famous for being an executive producer of The Dick Van Dyke Show and The Andy Griffith Show. And so, the two leading scientists on the CBS sitcom both take their names from the influential Hollywood guru.

Penny's character was originally called Katie in an unaired pilot, and she was played by Amanda Walsh. Walsh played a "hyper-sexual, a bit more raunchy version of Penny." However, the test audience felt overprotective of the guys and didn't like Katie. 

According to Glamour, there's only one set of stairs on set. So, every time an actor walks up and down a set of stairs, it's the same staircase, but "redressed" as different floors of the building. Ah, TV magic!

Show writer Stephen Engel would set up a recurring practical joke that involved taping a hallowed out grapefruit back together.  "I'd open it up and [he] would say 'bazinga," executive producer Bill Prady told Entertainment Tonight. "It was Stephen's word for gotcha." And thus bazinga was born.

Raj's characteristic of only being able to talk to women when he's drunk is based upon EP Bill Prady's old coworker, who has the same problem. 

Except for the pilot, which is titled "pilot."

While we've heard most characters' last names ... Penny's remains a mystery (well, her maiden name). Executive producer Steve 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."

Any guesses?

If you look closely, the glasses Leonard wears don't have lens inside; they are just frames because Johnny Galecki (unlike Leonard) doesn't have bad eyesight.

Who could ever mistake Bernadette's high-pitched voice? Turns out, Melissa Rauch impersonated her mother's voice for the character. "Only without the Jersey! Tonally, it's very similar," the actress said at the PaleyFest panel in 2013.

Originally, the show was called "Lenny, Penny and Kenny" before creators came up with The Big Bang Theory.

No wonder Leonard and Penny have lots of chemistry — the actors actually dated in real life during the show! "It was such a huge part of my life and no one knew about it," Cuoco previously told CBS Watch in 2010. "It was a wonderful relationship, but we never spoke a word about it and never went anywhere together."

The original pilot was for an entirely different show. According to IMDB, the unaired pilot introduced two awkward scientists, Leonard and Sheldon, who share an apartment and invite a drunk girl Katie to stay with them because she had nowhere else to go. The characters of Leonard and Sheldon were the only part the creators kept.

UCLA professor David Saltzberg makes sure the science is accurate in the script each week. He looks into every formula to ensure accuracy. According to NPR, Saltzberg studies high-energy particle physics and high-energy neutrino astronomy.

Turns out, Jim Parsons is far from Sheldon Cooper. In an interview with Time, Parsons admitted that when in college, he actually failed a meteorology class.

 According to Radio Times, the number often seen on Sheldon's shirts are a nod to the year that star Jim Parsons was born: 1973. 

A tiny blink-and-you-missed-it detail from Penny's apartment showcases the camaraderie behind-the-scenes, as the photos on the fridge were taken of the Big Bang Theory cast and crew.

If you recall, Amy's apartment number is 314. As in the first three digits of Pi.

Sheldon often wears The Flash t-shirts, but have you spotted the Big Bang Theory-themed clothing sported by Cisco Ramon (Carlos Valdes) in the CW's adaptation?

During the musical sequences of Big Bang scenes, there's no fake-playing necessary! All the actors have actually learned to play their character's go-to instruments. Bialik plays the harp, Parsons the theremin, and Galecki the piano.