A new walker variation means new problems on the final season of The Walking Dead. “I’ve heard stories of walkers that can climb walls and entryways. I was rarely sure assuming that they were just stories,” said Aaron (Ross Marquand) in the show’s San Diego Comic-Con trailer, revealing what appeared to be zombies with brraaiinnss. In any case, before The Walking Dead ends with its last episodes, premiering October 2 on AMC, the zombie show is going back to the beginning: by bringing back “smart” walkers not seen on the flagship since its first season.

“There’s a reason why he’s saying those specific words,” showrunner Angela Kang teased in an interview with EW about Aaron’s ominous discourse. “Furthermore, it will cause some massive problems for our kin.”

The trailer showed just that: a walker climbing a wall and a turning door handle. “We’ve seen that on the show previously,” noticed AMC’s Walking Dead Universe boss substance officer and chief maker Scott M. Gimple, referring to walkers who displayed more human-like conduct in the show’s earliest episodes.

In one, a young lady walker picks up a bloodied teddy bear before Morgan’s (Lennie James) vivified spouse tries opening the way to their family home. In another, eager for flesh walkers scale a door and smash a retail chain window with a stone to get inside.

“It has escaped discussion on the show. You can see in the trailer, there’s some unique way of behaving, yet this isn’t any sort of reinvention,” Gimple said. “Addressing something is inside the show as of now. The calls are coming from inside the house.”

Chief and leader maker Greg Nicotero, who has served as The Walking Dead’s special cosmetics effects master since 2010, explained the inconsistencies in walker conduct: producers were still working out which kind of walkers were roaming in the true to life variation of maker Robert Kirkman’s comic book.

“Actually we hadn’t exactly sorted out yet what the rules for the zombies were. They were also a piece faster in the first episode when they chased Rick down the street on his horse,” said Nicotero of the pilot from that point showrunner Candid Darabont, whose walker rules didn’t live on in later seasons. “There’s another scene where Glenn and Rick are being chased down the back street and they start climbing up an emergency exit. What’s more, there are walkers climbing up behind them. We were still figuring it out. In any case, we concluded that it was an open door.”

As for why these walkers seemingly disappeared for quite some time, Nicotero explained, “We sort of played into that as assuming there may be certain walkers in certain regions that could have various abilities that we truly haven’t seen previously. We’re kind of playing into the possibility that some of these are out there and they’re just encountering them now.”

Over on The Walking Dead: World Past, CDC virologist Dr. Edwin Jenner (Noah Emmerich) — a person also not seen since the first season of The Walking Dead — coined the expression “variation cohorts” for French walkers who appeared to be faster and stronger than standard roamers. According to Gimple, that is less to do with The Walking Dead and even more an issue for Daryl Dixon (Norman Reedus), who will find himself in France in his solo spinoff series taking spot after the flagship series ends.

“These are very distinct environments and very distinct landscapes,” Gimple said of France and Ohio, where the Ward is situated on The Walking Dead. “[The World Past coda] was out in Europe. In any case, we realize someone who’s going to be out there, so he could have his hands full.”

The Walking Dead: The Last Episodes begin October 2 on AMC and with a two-episode debut on AMC+.