Bazinga!The Big Bang Theorycelebrates its 15th anniversary on Sept. 24.
The concept was simple.
The result was anything but.

Bill Prady and Chuck Lorre.Frazer Harrison/Getty
ENTERTAINMENT WEEKLY: This September marks 15 years sinceThe Big Bang Theorypremiered.
So, I want to know all about the pilot.
How did all of this come together?

Jim Parsons, Johnny Galecki, and Chuck Lorre.WarnerMedia
How did you create that first episode?
She’s dangerous in a way and wasn’t very nice to the guys.
PRADY:Theyhatedher, but what was amazing was that they were defending Leonard and Sheldon so much.

Behind the scenes of ‘The Big Bang Theory’.WarnerMedia
LORRE:Yeah, we didn’t realize early on that the audience viewed them as children.
They were very naive and childlike, regardless of how intelligent they were.
They were very vulnerable, and the audience didn’t want a toxic presence around them.

Kaley Cuoco and Kunal Nayyar on ‘The Big Bang Theory’.WarnerMedia
Who played the original Penny?
PRADY:The actress was Amanda Walsh, and she did a great job playing that character.
LORRE:She was terrific in the role, but the role was misconceived.

Kaley Cuoco and Mayim Bialik on ‘The Big Bang Theory’.WarnerMedia
It was our responsibility.
Our script didn’t fully realize what our possibilities were.
Let’s just spend a half hour diving into the lives of these brilliant misfit characters."

Shooting ‘The Big Bang Theory’.WarnerMedia
When you think about it, the plot of the second pilot is pretty simple.
So, she gives him a task, he fails at it, and then they all eat dinner!
Leonard says, “Should we invite her to lunch?”

Shooting ‘The Big Bang Theory’.WarnerMedia
And Sheldon responds with, “To what end?”
To me, Leonard’s struggle was always that Penny was like the outside world.
She was like, come out dancing, come out and see things.
LORRE:Penny was a risk.
LORRE:Sheldon had a very circumscribed life.
But Penny was this random element that was introduced into their lives and changed them forever.
Sheldon was never able to have the rigid order he wanted after her arrival.
Somehow, in our discussions, that moved out of the Sheldon character and into Raj.
LORRE:Yeah, we created two characters out of that one guy.
And then she would leave, and he would start talking again.
Obviously, we started noticing it.
It’s a real thing, selective mutism.
It’s an anxiety condition.
He was just so anxious around women that his solution was to not talk.
LORRE:And Penny is the one who cured Raj.
She was the pivot point for all these characters.
But she also introduced him to Bernadette.
She impacted all these characters in such a major way.
Being different seems to be an ongoing plot equipment for almost every character in the show.
Was that at the forefront of your mind when creating the series?
That’s something we’ve all felt and can understand.
I think most people can identify with it on some level, that alienation, even popular people.
PRADY:Chuck used to talk about the difference betweenA Beautiful MindandRevenge of the Nerds.
But to me, it was the most interesting place.
People had interests in random things like Tuvan throat singing and they’d want to tell youallabout them.
LORRE:That’s you, Bill!
I think we all watched that and understood something remarkable was happening.
It was an astounding moment I’ll never forget.
PRADY:I lovethe episodewhere Sheldon doesn’t like that Leonard is dating Raj’s sister.
She was a lawyer and kept finding loopholes in the roommate agreement and was using it against him.
To me, that was this great nerd explosion.
LORRE:That’s when he hugged Penny.
It was the first time he laid a hand on her.
That was a big character breakthrough moment, he was so alienated up to that point.
How did that evolution happen?
LORRE:Again… it’s Penny.
Because, originally, Amy’s first love was Penny.
She wanted girlfriends and a social life with other women because she was denied that as a child.
That was the first breakthrough with her character.
It wasn’t with Sheldon, it was with the girls.
She got to experience sleepovers and shopping and all those things her mother hadn’t let her do.
So that’s part of the evolution, but she also pulled Sheldon along.
LORRE:We thrust unconditional love at him and he finally melted.
It took about five years, but he did eventually melt!
The eraBig Bangstarted in vs. the era it ended in vs. now are all so different.
PRADY:So muchhashappened.
We’ve lived through so many things.
LORRE:Sheldon would have loved the pandemic.
Being able to stay at home and not deal with the world?
He would have thought it was perfect.
I can already hear her scream, “Don’t tell me about my job!”
LORRE:We would have done two seasons with Sheldon in a hazmat suit.
Like the John TravoltaBoy in the Bubblemovie!
The closure it brought was astonishing.
It’s hard to imagine reopening the story after that.
LORRE:I agree, I don’t think we left anything undone.
That was as close to a perfect finale as we could have ever dreamt of doing.
PRADY:The story for that finale really starts about four episodes before.
The last four or five episodes are actually just one giant story.
But would I like to stand on a stage someplace and watch those characters again?
Can I imagine a way to do it?
Yeah, I get choked up just thinking about it.
But I don’t know how we’d do that.
Alright, final question.
I want to know a behind-the-scenes story that you’ve never told anyone before.
PRADY:I have a great one.
So on the set we had tons of antique scientific equipment.
People always ask what that thing on the wall post was.
It was this wooden box, which was actually an antique Geiger counter.
Throughout the show’s run, really famous scientists visited the set all the time.
LORRE: Steve actually came back and visited like five more times after he filmed his episode.
He’d come by and just hang out.
PRADY:So, one day this super famous physicist was visiting.
We say, “Yes, that is.”
He said, “I wonder if there’s uranium in that.”
And then he removed a piece of uranium from the Geiger counter and left!
[Laughs]
LORRE:Yeah, that’s kinda like a class-action suit waiting to happen.
We had uranium on the set ofThe Big Bang Theory.
PRADY:Should we not print that?
[Laughs]
LORRE:[Laughs]I don’t know, Bill!
That’s great Bill, thanks for sharing that.
Turns out, there were 4,000 people who came, It was standing room only.
People camped in tents the night before.
They were crying tears of joy to be getting an autograph from Jim Parsons.
The characters meant so much to them that it was like getting autographs from The Beatles.
PRADY:Yeah, the difference between the first and second year was incredible.
We even walked the Comic-Con floor that first year.
The cast would get looks, but they were still able to blend in.
I remember because Johnny wanted to walk around and see the G.I.
That autograph signing you’re talking about was actually the second year.
They couldn’t move without security.
I remember thinking, “A year ago, we walked on the floor looking for G.I.
Joe, and now this.”
LORRE:There was a very personal connection between fans and the cast.
They had significance in people’s lives, it was remarkable.
We connected with a lot of people who felt alienated, the same way these characters did.
They wanted to be a part of life, but they didn’t know how.
And these characters said, here’s how you create your own community and your own family.
They showed the world that nobody has to be alone.