Cuoco and Galecki’s characters, Penny and Leonard, ultimately got married, and had at least one child that we know of. The actors, of course, did not, but they did date exclusively for two years, from 2008 to 2010. 

In fact, much of the authenticity in their relationship onscreen was driven by the love and respect Cuoco and Galecki shared in real life.

And when the offscreen relationship ended, their professional commitments and even their TV dialogue helped them heal. They developed a friendship that runs deep—and is in many ways the true love story of the show.

Three plus years after Big Bang wrapped production, the duo are as tight as ever, which was made evident by the many Zooms that they did together for this book in order to pay homage to Penny and Leonard—and each other.

Ahead, excerpts from a chapter in The Big Bang Theory: The Definitive, Inside Story of the Epic Hit Series.