7 things you didn't know about Kaley Cuoco

Kaley Cuoco at the 17th Annual Instyle and Warner Bros. Pictures Golden Globes After-Party in 2016. (Reuters)

"Big Bang Theory" star Kaley Cuoco has become a Hollywood "it girl" over the past few years.

You may think you know almost everything about the "Big Bang Theory" actress, but think twice.

Here are some surprising facts about the sitcom superstar:

1. Kaley wasn't the first choice for 'The Big Bang Theory'

Kaley Cuoco (C) accepts the award for favorite network TV comedy series with the cast and crew of "Big Bang Theory" at the People's Choice Awards 2016 in Los Angeles, California January 6, 2016. REUTERS/Mario Anzuoni - RTX21CMJ (Reuters)

Believe it or not, the main female character in the show was originally going to be played by Canadian actress Amanda Walsh.

According to the International Business Times, Walsh starred in the original pilot as the character Katie, but CBS rejected the show.

Eventually, the network picked up the show when Cuoco replaced Walsh as the now-popular character, Penny.

The rest is history.

2. She finished high school at 16

Actress Kaley Cuoco, start of the television comedy series "8 Simple Rules for Dating My Daughter" poses as she arrives at the sixth annual "Teen People" 25 Hottest Stars under 25 party in Hollywood May 5, 2003 as a guest. The list features the top young stars in film, music and television. PP03050020 REUTERS/Fred Prouser FSP - RTRMZHO

You can add Cuoco to the list of smart Hollywood celebrities.

According to IMDB, Cuoco was home-schooled and earned her diploma early at 16.

3. Kaley has a knack for horseback riding

Actress Kaley Cuoco arrives at the 58th Grammy Awards in Los Angeles, California February 15, 2016. REUTERS/Danny Moloshok - RTX2731H (Reuters)

Cuoco has been an avid horseback rider and trainer since she was 15 years old.

She recently posted a pic on Instagram of her kissing her horse Bojangles alongside her fiance, Karl Cook. She wrote, "Not sure who I'll miss more."

4. Cuoco sings!

At the age of 25, Cuoco faced a scary fall during a horse riding accident.

While she was in the hospital with a leg fracture, Cuoco and her then-boyfriend Christopher French, of the group Annie Automatic, sang "Somewhere Over the Rainbow.”

The couple eventually recorded the song for the Human Society of the United States in support for animal adoption.

5. She is a former nationally-ranked tennis player

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According to IMDB, before becoming an actress, Cuoco was a notable amateur tennis player who won several matches in the junior leagues.

Cuoco was reportedly ranked sixth during the 2000 USA National Open Championship amongst junior and college tennis players. She still plays recreationally.

No wonder she connected with her ex-husband, Ryan Sweeting, a professional tennis player.

6. Kaley was Ellen DeGeneres?

Executive Producer Ellen DeGeneres speaks about the NBC television show "One Big Happy" during the TCA presentations in Pasadena, California, January 16, 2015. (Reuters)

That's right — in DeGeneres' sitcom during the 1990s, "Ellen," Cuoco played a younger version of the comedian.

In Episode 6 of Season 4, Ellen and her childhood friend, Paige, played by Joely Fisher, go to the same summer camp they went to when they were kids.

With her hair cut short like Ellen, Cuoco plays the flashback version of Ellen, as DeGeneres and her friend reminisce.

7. She voiced a dog

Actress Kaley Cuoco arrives at the 2015 Kids' Choice Awards in Los Angeles, California March 28, 2015. REUTERS/Danny Moloshok - RTR4VAOX (Reuters)

Cuoco was the voice behind the main character on the animated show "Brandy & Mr. Whiskers," on Disney Channel.

The show aired for two seasons, from 2004 to 2006. The series followed Brandy, a tomboyish 14-year-old dog and her rabbit friend, Mr. Whiskers.