“Stuart Fails to Save the Universe” saved its biggest mind-bender for last.

The Season 1 finale sees Stuart, Denise, Bert, and Kripke escape the DC Comics-inspired universe they entered in Episode 9, only to find themselves stranded in a vast, empty void. There, they learn of a menacing, otherworldly entity that is none too pleased with the foursome for repeatedly altering the course of human history.

But things get even stranger from there.

Stuart and Co. ultimately wind up in what appears to be the real world, where they stumble onto the set of the multi-camera sitcom “Stuart Fails to Save the Universe” — which essentially serves as a placeholder for “The Big Bang Theory” — and discover that not only are they fictional characters, but there are actors who look exactly like them playing those characters on television.

When TVLine first spoke with series stars Kevin Sussman and Lauren Lapkus at a pre-season junket in July (see above), both recalled just how surreal it was to film the meta twist on a recreation of the old “Big Bang” comic book store set.

“It’s bizarre. It’s like being back in time,” Lapkus said of seeing the set transformed back into a multi-camera stage, complete with a live studio audience.

For Sussman, returning to that version of the comic book store was somehow even stranger than walking onto the reimagined “Stuart” set at the start of production. “That was something that we actually had experienced eight years ago,” he explained.

Then there’s the existential crisis the finale leaves dangling: How do Stuart, Denise, Bert, and Kripke move forward after learning that they’re fictional characters? Lapkus suggested there may be some wiggle room. Perhaps they simply visited another universe — one where they happen to be characters on a TV show. Still, “you saw another person playing you,” she reasoned. “That feels like that’d be hard to let go of.”

Sussman, meanwhile, went full “Inception,” questioning whether the actors playing those fictional characters might themselves be fictional characters, and whether Season 2 could pick up with those versions of Stuart and Denise instead.

But that’s not the finale’s only lingering mystery: Throughout Season 1, someone — or something — had been attempting to communicate with Stuart across every universe he visited. Then came the revelation of the otherworldly entity that had Kyle and Trevor doing its bidding.

When TVLine asked co-creators Chuck Lorre, Bill Prady, and Zak Penn in July whether they knew the answer to that mystery — and whether Season 2 would provide one — their answers were considerably less forthcoming.

“Say yes,” Penn instructed.

“Say yes and see if he believes it,” Lorre joked.

Prady offered another possibility: “Each of the three of us know, we’re each holding a different idea in our head, and none of us has told the other — which I think is probably true.”

“It’s a great question that we can’t answer,” Lorre concluded.

More recently, TVLine reconvened with Lorre, Prady, and Penn — who joined via Zoom from the Season 2 writers’ room, which started back up September 14 ahead of an anticipated January or February production start and a 2027 premiere — to go deeper on the finale.