The Big Bang Theory did not start off with a bang 12 seasons ago.

Its first season was abbreviated by a 100-day writers strike and ended with the CBS comedy ranked 68th in the Nielsens for 2007-08.

As the show about Caltech scientists and their friends and families wraps up its 279-episode run with a two-episode finale on Thursday, May 16, it’s television’s most-watched comedy.

And deservedly so.

I wasn’t so sure in 2007, when I included Big Bang in a fall preview list of shows “that might improve on further acquaintance.” I’d likened Kaley Cuoco’s not yet fully developed character, Penny, to Three’s Company’s Chrissy, but noted that I’d been told, "Caltech physics students have seen some of the math on display in the pilot and deemed it not out of line. And [co-creator Chuck] Lorre, who also created Two and a Half Men, has been known to work wonders with fractions.”

I was right about the math, at least.

I’m not sure how much physics most of us have learned in the last 12 years, but there are plenty of other takeaways from the success of The Big Bang Theory:

1. It can take time to grow a hit. “I’ve been really fortunate” to get that time, Lorre said when I visited the show’s Warner Bros. set with a group of reporters in February. "We got to learn about what the show was by doing the show, by making the show. The show taught us what it was. The audience taught us what it was.”

"The Big Bang Theory" cast as we're used to seeing them -- talking over takeout. From left: Simon Helberg, Melissa Rauch, Kunal Nayyar, Mayim Bialik, Jim Parsons, Johnny Galecki, and Kaley Cuoco.
Michael Yarish/Warner Bros. Entertainment
"The Big Bang Theory" cast as we're used to seeing them -- talking over takeout. From left: Simon Helberg, Melissa Rauch, Kunal Nayyar, Mayim Bialik, Jim Parsons, Johnny Galecki, and Kaley Cuoco.

2. There’s a lot to be said for an expanding universe. Lorre said he never considered Penny dumb, just more socially and emotionally adept than her male neighbors, Sheldon Cooper (Jim Parsons) and Leonard Hofstadter (Johnny Galecki), and their friends Raj Koothrappali (Temple grad Kunal Nayyar) and Howard Wolowitz (Simon Helberg). But she did seem to get smarter, and adding more women to the mix — particularly Mayim Bialik as neurobiologist Amy Farrah Fowler and Melissa Rauch as microbiologist Bernadette Rostenkowski — both added to the comedy and made Penny’s differences seem less about gender. “We saw where we’d fallen short,” Lorre said. “We saw where we hadn’t really done our jobs, and we tried to broaden the show. Legitimately, not pandering. But female scientists — of course. You know, duh.”

3. Smart humor and bathroom humor can coexist. The same show that brought on Nobel laureates Kip Thorne, George Smoot, and Frances Arnold to play themselves in an episode in April has never been above the kind of jokes about bodily functions that speak to a lot of people’s inner 8-year-olds.

4. We like to watch families. The casting of, and writing for, the main characters’ parents — starting with Laurie Metcalf and Christine Baranski’s guest shots as Sheldon and Leonard’s mothers — has done a lot to explain how they came to be who they are. But even before the show started pairing off its characters, they’d formed a family. “The lesson I’ve learned over and over again, going back to when I was a writer on Roseanne [is that] all these shows that work seem to have an underlying theme of family and affection ... whether or not it’s biological relations or friendships," Lorre said. “Even Seinfeld, where the characters were constructed, I think, to be abrasive, they were there for each other.”

Cast members and producers of CBS's "The Big Bang Theory" took a selfie on the show's Warner Bros. set in February, when the stage that's been home to the record-breaking comedy was renamed in its honor. From left: star Kaley Cuoco, executive producers Steven Molaro and Chuck Lorre; stars Melissa Rauch, Kunal Nayyar, Mayim Bialik, Simon Helberg, Johnny Galecki, and Jim Parsons; executive producer Bill Prady; star Kevin Sussman.
Courtesy of Warner Bros.
Cast members and producers of CBS's "The Big Bang Theory" took a selfie on the show's Warner Bros. set in February, when the stage that's been home to the record-breaking comedy was renamed in its honor. From left: star Kaley Cuoco, executive producers Steven Molaro and Chuck Lorre; stars Melissa Rauch, Kunal Nayyar, Mayim Bialik, Simon Helberg, Johnny Galecki, and Jim Parsons; executive producer Bill Prady; star Kevin Sussman.

5. There’s a place on television for brilliant people who don’t solve crimes or cure the sick. With all due respect to Sherlock Holmes (both the CBS and PBS versions) and ABC’s The Good Doctor, it’s nice to see people with high IQs having a few other options.

6. Not every difference requires a label. Is Sheldon on the autism spectrum or is he just quirky? In resisting a diagnosis, the writers forced us to deal with him as a character, not a condition. Not everyone’s happy with that decision — and I understand the desire for representation — but it did keep him from being frozen in place in the minds of people who might not have believed progress is possible for someone with his challenges. “What happens in this show over 12 years is that these people around him socialized him,” Lorre said, identifying the episode in which Sheldon hugged Penny after she gave him a napkin signed by Leonard Nimoy as a turning point. "Because these people never gave up on him, he became more dimensional.” At the same time, "he’s still Sheldon. And that’s the magic trick of TV comedy. … Archie Bunker has to stay Archie Bunker.”

Physicist Stephen Hawking with actor Jim Parsons on the set of CBS’ “The Big Bang Theory” in 2012, when Hawking first appeared on the show
Sonja Flemming/CBS
Physicist Stephen Hawking with actor Jim Parsons on the set of CBS’ “The Big Bang Theory” in 2012, when Hawking first appeared on the show

7. It’s not just the guest stars — it’s how the guest stars are used. Casting physicist Stephen Hawking as himself was a coup, but making him part of the comedy was a triumph.

8. It’s never too late to get Bob Newhart an Emmy. As crazy as it is that the comedy legend, nominated nine times, won his first (and so far only) Emmy for his first appearance as Sheldon and Leonard’s childhood idol “Professor Proton,” it’s no accident that he chose to guest-star on this show. “Chuck [Lorre] and I have been talking about this for a long time, and we [could] never agree on the show,” Newhart told me in a 2013 interview. “I wasn’t a big fan of Two and a Half Men, but I am a big fan of The Big Bang Theory, and I thought it was extremely well-written and it’s done in front of a live audience, and those were the two requirements that I had.”

Among "The Big Bang Theory's" greatest guest stars was comedy legend Bob Newhart, here with Jim Parsons and Kaley Cuoco in a 2013 appearance on the show, where he played the retired "Professor Proton," who'd hosted Sheldon and Leonard's favorite childhood TV show.
Michael Yarish/Warner Bros. Entertainment
Among "The Big Bang Theory's" greatest guest stars was comedy legend Bob Newhart, here with Jim Parsons and Kaley Cuoco in a 2013 appearance on the show, where he played the retired "Professor Proton," who'd hosted Sheldon and Leonard's favorite childhood TV show.

9. It’s OK to end the will they/won’t they suspense. Maybe it didn’t work on Cheers or Moonlighting, but the story of Leonard and Penny is a happier, funnier one. As Galecki told reporters in February, he never worried when the characters married, because most of the show’s writers are married, “so they were able to bring their own life experiences to Leonard and Penny’s relationship. ... The same way when Bernadette and Howard had a baby — you know, the majority of the writers are parents, as well. They get to bring that side of their lives now into the show.”

10. How science works. Though I can’t begin to explain Sheldon and Amy’s “super asymmetry” theory — and not just because it apparently isn’t real — I appreciate the glimpses we get of the not terribly glamorous aspects of scientific discovery, like checking citations and chasing funding. Off screen, the show has expressed its appreciation by helping to underwrite the educations of UCLA students in the fields of science, technology, engineering, and mathematics through the Big Bang Scholarship Endowment.

11. The Oscars and the Emmys aren’t the only awards people get worked up about. I don’t know whether they’ll win, but Sheldon and Amy’s quest for a Nobel Prize in physics has been as eye-opening as it’s been hilarious.

12. It’s best to leave people laughing. Twelve seasons — and a lifetime, perhaps, in syndication — is better than letting the audience exit first.

The Big Bang Theory. 8 p.m. Thursday, May 16, CBS.

The Big Bang Theory: Unraveling the Mystery. Kaley Cuoco and Johnny Galecki host a retrospective that follows the season finale of The Big Bang Theory spin-off Young Sheldon. 9:30 p.m. Thursday, May 16, CBS.