'The Walking Dead' chief says a space spore did not start the zombie apocalypse on the show, and we may never learn what caused it

• On "The Walking Dead: World Beyond," a marine tells his comrades he heard the zombie virus was started because of a space spore.
• "World Beyond" showrunner Matt Negrete told Insider they did not reveal the cause of the zombie apocalypse. Rather, it was a nod to the comics.
• "TWD" universe chief content officer Scott Gimple told Insider "there are no immediate plans" to reveal what caused the walker apocalypse.

A "Walking Dead" spinoff series recently appeared to tease that a space spore may have started the zombie apocalypse, but "TWD" universe chief content officer Scott Gimple says that's not the case.

"I can say it's not canon," Gimple told Insider of a moment on episode seven of "The Walking Dead: World Beyond" in which a marine said he heard "it came back in a rocket, that it started in space."

"You know, never say never on certain things, but that wasn't a reveal as much as much of a reference," Gimple added.

The space spore mentioned in 'TWD: World Beyond' was just a nod to the comics

"World Beyond" showrunner Matt Negrete also told Insider the space spore moment was just an Easter egg.

"It really was just a nod to the comics," Negrete said.

In "TWD" comics, creator Robert Kirkman famously added a special ending to issue No. 75 in which a non-canon ending showed aliens were responsible for the zombie apocalypse.

"That was a line that Eddie Guzelian, who wrote that script, put in there," Negrete continued. "And then I heard months later after we shot [the scene] that Robert Kirkman had made a tweet about a space spore, so it really was like this random coincidence/timing."

Negrete is referencing Kirkman's tweet from January 2020 in which the "TWD" creator joked that the zombie virus was caused by a space spore.

—Robert Kirkman (@RobertKirkman) April 24, 2020

"I think people were maybe thinking we did that as a nod," Negrete said. "We actually wrote that before Robert ever tweeted that, even though that was always kind of a joke from the comic early on. It was just one of those funny things that all kind of happened to tie in together."

When Insider told Negrete we thought the reverse — that maybe Kirkman had read the script and then tweeted about it — Negrete said that was certainly possible.

"We haven't spoken about that," Negrete said. "I would say that's possible. It's funny how it all lined up. I wouldn't rule that out."

So if it wasn't a space spore, then what started the zombie apocalypse?

It definitely seems like there was some sort of virus. The characters on "World Beyond" seem hard at work on some type of cure. Why else would they be running tests on so many of the undead?

Gimple emphasized the important thing about "TWD" apocalypse is that there is so much uncertainty about it. That's a huge part of the show's mythology.

"I will say we're working on some things that feature the beginning of the apocalypse in various ways, in various stories," Gimple said. "There's like three or four different things that reference it that we're working on right now and the lack of information and certainty is such an important part of what happened to the world of 'The Walking Dead.'"

"The fact that alien spores could be entertained and the fact that I will not completely take it off the table is a feature, not a bug of the walker apocalypse," Gimple added.

Kirkman has previously said that he knows exactly what started the zombie apocalypse in "TWD" comics, but said he never planned to tell anyone the cause because "it's dumb."

When asked if we'll ever learn what really started the walker apocalypse at some point, Gimple made it sound unlikely.

"I think we could get hints in different directions," Gimple said. "I don't think we're going to give it to you with certainty anytime soon."

"That said, we're planning on telling different sorts of 'Walking Dead' stories for years and years and years," Gimple added. "So, who knows? But, there are no immediate plans to reveal that. I think that's an important thing to say."