Sheldon Cooper having sex? At one point, the very notion would have sounded preposterous. Yet after more than five years of his peculiar courtship with fellow scientist Amy Farrah Fowler, the producers felt they had organically reached the juncture to make Thursday’s much-ballyhooed episode a logical next step.

Although there’s a fairly rich trove of analysis devoted to Sheldon’s sexuality – and co-creator Chuck Lorre once said that the character simply chose not to participate in that arena – showrunner Steve Molaro stressed that the writers didn’t see the sex plot (and SPOILER ALERT if you haven’t watched) as selling out the character.

“I don’t think we ever tapped into Sheldon being asexual enough that we ever thought it would be a sellout when we got to this point,” Molaro said. “It was something we talked about early on, but once he met and started dating Amy – which has now been 5 ½ years – it just sort of evolved naturally. So it wasn’t a real concern of ours.”

Much of the current season has focused on the relationship between Sheldon (Jim Parsons) and Amy (Mayim Bialik), who broke up with him, leading to a reconciliation and greater intimacy between them. That concluded with Sheldon deciding to sleep with her for her birthday, even passing on an opportunity to see an early showing of “Star Wars: The Force Awakens,” the viewing of which was presented as a near-orgasmic experience for his friends.

Asked if Sheldon-Amy had taken center stage because there have been so many ups and downs between the now-married Leonard and Penny, Molaro said, “We’ve been through a lot with all of the characters, and all of the relationships. I think Amy was justified in taking a step back and thinking about what she was doing with Sheldon. … There is quite a lot of patience required to be with someone like Sheldon.”

As for juxtaposing Sheldon and Amy’s moment with “Star Wars” – which just happens to coincide with the episode – Molaro noted, “Over the past few years it had already been set up that Bob Newhart, as Arthur, would appear to Sheldon dressed in Jedi robes. … So for quite a while, we knew if and when Sheldon was going to be intimate with Amy, we would love Bob Newhart to come back to help him navigate that in a fatherly way. That ‘Star Wars’ aspect of it had been kind of floating around in the writers room already, and when we knew the new ‘Star Wars’ movie was coming, that helped those planets align even more.” (Incidentally, Arthur’s joke about wanting to reappear in Angie Dickinson’s bedroom was “not our first Angie Dickinson reference on ‘The Big Bang Theory,’” Molaro noted, citing an earlier episode with James Earl Jones.)

The actual sexual encounter, meanwhile, was unexpected in at least two ways. First, Amy was apparently quite satisfied; and second, Sheldon made clear that he viewed “coitus” as an annual event – something that would be reserved for her birthdays in the future.

“As far as this being some sort of sellout or giant shift in the character, I think it’s lines like that that allow us to have such a momentous occasion, but it still can feel very much like Sheldon and Amy – Sheldon saying that we did this thing, but we’re only going to do it once a year is an example of us holding the character intact, even when something this monumental happens,” Molaro said.

Long-running sitcoms have a history of advancing relationships in an effort to stay fresh – witness later seasons of “Friends” – but Molaro maintained “Big Bang’s” milestones have been rooted in reality for characters in this life phase.

“There’s still quite a bit of dynamics between these seven characters that have yet to be explored,” he said. “They’re living their lives, and they’ve been growing for eight and half years now. Often in your life, there’s small events that happen. But a few times a year, someone does get married, or somebody gets pregnant. I think that ratio, the way we do it so far, kind of reflects real life, and happens at those ages where these characters are. So it’s nice to have these tent-pole events, and then there’s the smaller, more typical stories that we’ve done.”

Given that, would a baby, for someone, be the next logical step? “Not at the moment,” Molaro said. “Babies have a tendency to alter the DNA of a show a little more than we’re looking to at this time. There are other avenues we want to explore before we get to the pitter-patter of little nerd feet.”

Despite considerable discussion and even scholarly dissertations about Sheldon’s eccentricities – and whether they might be associated with some sort of condition, such as Asperger’s syndrome – Molaro said, “Sheldon the character has never gotten any kind of diagnosis. As far as we’re concerned, with his quirks and all, he’s just Sheldon to us.”

“Big Bang Theory” has already been renewed through next season, and given its importance to CBS and value to Warner Bros. Television, there will be strong incentives to keep the show alive beyond that. In terms of whether there’s enough material to carry through a 10th season and potentially beyond, Molaro said, “We still have a long way to go that we’re still excited about.”