Inside The Big Bang Theory: TV's Most Popular Sitcom

The cast of The Big Bang Theory

09/20/2014 AT 07:35 PM EDT

Before the cast of The Big Bang Theory can get on with the business of portraying America's favorite eggheads (and one foxy, out-of-work actress), there is a customary ritual that always precedes the reading of the very first script of the season.

It usually starts with a simple question: How did you spend your summer?

Faster than you can bust out a Bazinga, details are shared in gleeful progression: Jim Parsons (Sheldon) became a Wimbledon groupie. Simon Helberg (Howard) nested at home with his second baby. Melissa Rauch (Bernadette) produced her first movie. Johnny Galecki (Leonard) jetted to Prague, Kunal Nayyar (Raj) hightailed it to India, and Kaley Cuoco-Sweeting (Penny) went all Edward Scissorhands on her hair.

"It's a lot like the first day back at school," explains Mayim Bialik (Amy).

"There's the sense that you've been gone a really long time. We miss working together. We miss each other! Even if we see each other in the summer, it's not the same as the kind of work we do together, because that's really the basis of how we all know each other.

It's also a major reason why The Big Bang Theory, which is about to begin its eighth season on CBS, is such a mammoth hit.

The show reaches more than 20 million viewers – this, in an age when other sitcoms struggle to stay on the air – thanks in no small part to its likable, nerdy ensemble.

"If you met all of these people, you would want nothing but good things for any of them. There isn't one in the bunch where you'd say, 'Oh, I hope this guy doesn't get too full of himself,'" explains the show's co-creator and executive producer Bill Prady.

"And when you've been together for nearly a decade, with marriages and babies, it's a family thing. If you talk about extended families, this one gets along a lot better than my real one."