The running theme for the cast and crew on the set of the final season of “The Big Bang Theory” is the idea that it’s the senior year of a 12-year sitcom school — which explains why the actors, writers and production team posted yearbook photos around the soundstage on the Warner Bros. lot in Burbank. 

Charged with leading the class to its graduation is Steve Holland, showrunner of the CBS comedy. The longest-running multi-camera sitcom will air a special hourlong series finale Thursday.

A few weeks before the goodbye, sitting in his orange-hued Warner Bros. office, Holland is calm, not at all the ball of nerves you might expect for someone attempting to bring one of television’s most successful shows to a satisfying end.

“Everyone is trying to enjoy this as much as they can,” he says. “I think we’re all incredibly aware of what a special thing this is.”

Holland joined the writing staff of “The Big Bang Theory” at the beginning of its third season, working his way up to executive producer in Season 9 and then showrunner by Season 11 in 2017 when Steven Molaro stepped down to head the show’s spin-off, “Young Sheldon.” Before his time on “The Big Bang Theory,” Holland wrote for Nickelodeon hallmarks including “All That,” “Kenan & Kel” and “iCarly” as well as other broadcast sitcoms such as “Less than Perfect” and “Rules of Engagement.”

He worked closely with Molaro and Chuck Lorre, the show’s co-creator (with Bill Prady), to craft the show’s send-off and on this mid-April day is in the throes of writing the finale. “The last scene we’ve known for a while — actually, the last two scenes,” he says, “But there was a lot of talk about what the first scene should be.”

Taking a break from the looming deadline, Holland talks about ending the show that’s been such a bang for CBS, how his work on Nickelodeon was a good training ground, and how writing for comedy today has evolved.

ON HOW NICKELODEON PREPARED HIM FOR PRIME TIME ON BROADCAST

I worked on and off at Nickelodeon for probably 10 years, and with all those shows, you had a lot of freedom to write what you wanted. But also, these staffs weren’t big, or the shows didn’t have tons of money — so it felt like a boot camp. You just had to write constantly. There weren’t 10 people there who were going to do it. There were three people or four people there, which just meant that you were constantly churning out drafts of things, stories of things, you know?

The goal was was the same. We never thought of it really as writing for kids. I mean, there were things that you obviously couldn’t do because it was a kid show, but it was never a thing of writing down (to the audience). If we thought it was funny and it was appropriate, we would put it in. That’s partly what made those shows so successful — it never felt like it was adults talking down to kids. I mean, we were all young too, but it was just us being goofy and silly, trying to make each other laugh.

ON JOINING AN ALREADY SUCCESSFUL TV STAFF

It’s intimidating, joining anything when a group of people have been together already. Luckily I wasn’t alone. Three of us that started at the same time. But yeah, you’re coming into the show that other people have gotten up and running — this show that sort of has a very science-y, heady bent. But you have to push past that and see if you have anything to offer. I had read Hawking’s “Brief History of Time” to prepare. As you can see from the office, I’m a “Star Wars” guy. I’m a comic book guy. I like science, but I’m not a science guy. I’m interested in it, I read about it, but that’s not a thing that I’m remotely an expert in. I also read (theoretical physicist) Richard Feynman’s books. It was the most homework I’ve ever done for a show. Just to kind of walk in and have at least a groundwork understanding.

ON HOW WRITING FOR COMEDY IS DIFFERENT NOW

I think the culture always shifts. I don’t know if the actual writing process has changed, but in good ways you certainly become aware of things that you didn’t even consider 10 years ago. Comedy is hard, and comedy doesn’t always date super well because the culture moves, and because jokes that are fresh you’ll see done over and over again. It’s a continually evolving process, sort of, hopefully, like society is always a continually evolving thing. In a good way, that also opens up new stories and new opportunities to tell different kinds of stories. If nothing changed, you would run out. But as long as people keep changing and shifting and growing, then it opens up new stories to tell.

ON THE AFTERLIFE OF A TV SHOW

(“The Big Bang Theory”) is obviously on a much bigger scale, but my first job was on “All That” and “Kenan and Kel.” I still meet people who are excited about that because it was a show that was a part of their life, that they had grown up on, and that they loved. When we were making “All That,” none of us were thinking this was a legacy show that people were gonna be talking about 20 years from now. We were all so young and just trying to figure out how to do this thing. With “Big Bang,” certainly, you’re aware of it. You’re aware of the impact that the show is having. And yeah, you just don’t get to be a part of that, that many times in a career. You’re lucky to get to be a part of it once. I hope it’s like an old friend that people are sad to see go but that they’ll bump into in reruns, and they’ll be like, “Oh, yeah, this was great.” And get to hang out and relive old times.