The Unexpected Age Difference Between Johnny Galecki And Kaley Cuoco From The Big Bang Theory

On "The Big Bang Theory," which aired from 2007 to 2019, Johnny Galecki and Kaley Cuoco portray characters who start as neighbors and friends but eventually fall in love, get married, and have a child together. Galecki plays Leonard Hofstadter, an experimental physicist who is Sheldon Cooper's (Jim Parsons) roommate at the beginning of the series and his best friend later on. Cuoco portrays Penny, an aspiring actress who lives in the apartment across the hall from Leonard and Sheldon. 

In addition to their characters falling in love on "The Big Bang Theory," Galecki and Cuoco dated for two years during the show, from 2008 to 2010, after a Season 1 scene led to their off-screen romance. Though the couple broke up nine years before "The Big Bang Theory" ended, they had to continue working together on the show, which couldn't have been easy to navigate. Luckily, a "Big Bang Theory" DVD special feature helped Cuoco and Galecki through their breakup.

While the ages of the characters are alluded to throughout the series, often, it's hard to tell how old the actors playing the roles are in real life — especially when they portray characters of different ages. In the case of Kaley Cuoco and Johnny Galecki, they are not as close in age as their characters appeared on "The Big Bang Theory."

According to Biography, Kaley Cuoco was born on November 30, 1985, and is currently 36, while Johnny Galecki was born on April 30, 1975, and is currently 47 (via IMDb). Therefore, there is approximately an 11-year age difference between the two "Big Bang Theory" actors. When the first episode of the CBS sitcom aired on September 24, 2007, Cuoco would have been 21, and Galecki would have been 32. 

Despite the age difference between the actors in real life, the characters they played in "The Big Bang Theory" do not share the same 11-year age gap. Penny is 21 at the beginning of the comedy series, the youngest main character on the show, and the same age Cuoco was in real life. In the series finale, Penny is 33 when she reveals her pregnancy. Although Cuoco was the same age as her character on the show, Galecki was slightly older than Leonard Hofstadter, who was 27 in the pilot episode and 38 in the series finale. This would mean that rather than an 11-year age difference between the actors in real life, there was a six-year age gap between the characters in "The Big Bang Theory."