Things you might not know about the ladies of 'The Big Bang Theory'

You may know the entire speedy “Big Bang Theory” theme song by heart, but that doesn’t mean you know everything there is to know about the lovely ladies from the series. Here are some surprising facts and things you might have missed about the female stars on CBS’ hit show:

1. Kaley Cuoco knows a thing or two about tennis

Kaley Cuoco-Sweeting from the CBS sitcom "The Big Bang Theory" arrives at the 66th Primetime Emmy Awards in Los Angeles, California August 25, 2014.  REUTERS/Lucy Nicholson (UNITED STATES -Tags: ENTERTAINMENT)(EMMYS-ARRIVALS) - RTR43Q10

Kaley Cuoco-Sweeting from the CBS sitcom "The Big Bang Theory" arrives at the 66th Primetime Emmy Awards in Los Angeles, California August 25, 2014. REUTERS/Lucy Nicholson (UNITED STATES -Tags: ENTERTAINMENT)(EMMYS-ARRIVALS) - RTR43Q10 (Reuters)

Kaley has been playing tennis since she was just 3 years old. Before she made it as an actress, she was a nationally-ranked amateur tennis player. She was married to professional tennis player Ryan Sweeting until they divorced in 2016.

2. Cuoco wasn’t the first choice for ‘Big Bang’

"The Hofstadter Insufficiency" -- Sheldon (Jim Parsons, right) and Penny (Kaley Cuoco, left) share intimate secrets while Leonard is away at sea, on a special one-hour seventh season premiere of THE BIG BANG THEORY Thursday, Sept. 26 (8:00 – 9:01 PM, ET/PT) on the CBS Television Network. Photo: Monty Brinton/CBS ©2013 CBS Broadcasting, Inc. All Rights Reserved.

"The Hofstadter Insufficiency" -- Sheldon (Jim Parsons, right) and Penny (Kaley Cuoco, left) share intimate secrets while Leonard is away at sea, on a special one-hour seventh season premiere of THE BIG BANG THEORY Thursday, Sept. 26 (8:00 – 9:01 PM, ET/PT) on the CBS Television Network. Photo: Monty Brinton/CBS ©2013 CBS Broadcasting, Inc. All Rights Reserved. (CBS)

Cuoco actually replaced actress Amanda Walsh, who filmed the show’s original pilot. That version of “The Big Bang Theory” didn’t get picked up by CBS, but the network gave the show the green light once a new pilot was made with Cuoco playing Penny.

3. Mayim Bialik is super smart in real life too

"The Locomotive Manipulation" -- Love is in the air when Sheldon (Jim Parsons, right) and Amy (Mayim Bialik, left) join Howard and Bernadette for a trip to wine country, on THE BIG BANG THEORY, Thursday, Feb. 6 (8:00 âÃÂà8:31 PM, ET/PT) on the CBS Television Network.  Photo: Michael Yarish/WBEI  ÃÂé 2014 WBEI. All rights reserved.

"The Locomotive Manipulation" -- Love is in the air when Sheldon (Jim Parsons, right) and Amy (Mayim Bialik, left) join Howard and Bernadette for a trip to wine country, on THE BIG BANG THEORY, Thursday, Feb. 6 (8:00 âÃÂà8:31 PM, ET/PT) on the CBS Television Network. Photo: Michael Yarish/WBEI ÃÂé 2014 WBEI. All rights reserved. (CBS)

Bialik, whose character is a brainiac, got accepted to both Harvard and Yale. She actually turned the Ivy League schools down and opted to attend UCLA.

4. Bialik doesn’t mess around with her hair

Actress Mayim Bialik.

Actress Mayim Bialik. (Reuters)

The actress, who considers herself to be a "hippie mama," created her own shampoo and avoids commercial cleaning products.

5. Melissa Rauch loves NPR

"The Prom Equivalency" -- When the gang recreates a high school prom on the roof the of the guys' apartment building, Sheldon feels pressure to participate in all the typical romantic traditions, on THE BIG BANG THEORY, Thursday, Nov. 6 (8:00-8:31 PM, ET/PT), on the CBS Television Network. Pictured left to right: Melissa Rauch and Simon Helberg Photo: Monty Brinton/CBS ©2014 CBS Broadcasting, Inc. All Rights Reserved.

"The Prom Equivalency" -- When the gang recreates a high school prom on the roof the of the guys' apartment building, Sheldon feels pressure to participate in all the typical romantic traditions, on THE BIG BANG THEORY, Thursday, Nov. 6 (8:00-8:31 PM, ET/PT), on the CBS Television Network. Pictured left to right: Melissa Rauch and Simon Helberg Photo: Monty Brinton/CBS ©2014 CBS Broadcasting, Inc. All Rights Reserved. (CBS)

Back in 2012, she explained to Sequential Tart, “My things have always been theater-related and comedy, or I'm a major NPR listener. I've always hung around nerds and felt more comfortable in that nerd domain.”

6. Rauch loved the show before she was cast

Melissa Rauch arrives at the 66th Primetime Emmy Awards in Los Angeles, California August 25, 2014.  REUTERS/Lucy Nicholson (UNITED STATES -Tags: ENTERTAINMENT)(EMMYS-ARRIVALS) - RTR43PQP

Melissa Rauch arrives at the 66th Primetime Emmy Awards in Los Angeles, California August 25, 2014. REUTERS/Lucy Nicholson (UNITED STATES -Tags: ENTERTAINMENT)(EMMYS-ARRIVALS) - RTR43PQP (Reuters)

When she joined the show as Bernadette in Season 3, Rauch was already a huge fan of the show, but she tried to play it cool on set. Variety reported earlier this year Rauch finalized her deal with Warner Bros. television to stay with the series. The deal will reportedly pay $500,000 per episode for 48 episodes.