Eli Roth’s The House with a Clock in Its Walls is a rare entry into the “spoopy” movie canon, melding horror and whimsical fantasy into an adventure palatable for the whole family. On paper, the adaptation of John Bellairs’ 1973 novel of the same name, sounds like major departure for Roth, whose past credits include Cabin Fever, Hostel, and the recent remake of Death Wish.

Except, even in a year that gave us Hereditary, Suspiria, Overlord, and the return of Michael Myers in Halloween, The House with a Clock in Its Walls delivered the single most disturbing image of 2018.

There is nightmare fuel, then there is the Animatronic Jack Black Baby, a pure injection of nightmare NOS.

The House with a Clock in Its Walls stars Jack Black as Uncle Jonathan, who, with the help of a heroic kid named Lewis (Owen Vaccaro), tries to prevent warlock Isaac Izard (Kyle MacLachlan) from using a magic clock to reverse time enough, so as to erase mankind’s blight on the cosmos. (Which, when you think about it, might not be a terrible idea?) While grappling over the MacGuffin (spoiler: The clock in the house is not in the walls, but below a boiler), Isaac slaps Uncle Jonathan with a spell that warps his own spacetime bubble and reverts him back to infant age. Which brings us to Animatronic Jack Black Baby, an image that would make Hieronymus Bosch quiver.

Veteran makeup artist Adrien Morot (X-Men: Apocalypse, TV’s Sharp Objects) tells Polygon that he was working on Roth’s version of Death Wish when he first read the script for The House with a Clock in Its Walls. He assumed that, in 2018, a baby version of Jack Back was an obvious candidate for CGI, but during a visit to Morot’s studio, Roth got his hands on the baby models created for Darren Aronofsky’s Mother!. The sight convinced the director that his Jack Black Baby needed to be an Animatronic Jack Black Baby.

“[Roth] basically spent half a day just playing with the remote controls, saying how he had never seen something as realistic in any effects shop,” Morot tells Polygon.

How does one create an Animatronic Jack Black Baby? For Morot, step one was imagining Jack Black as a baby with the power of Photoshop.

“It, uh, looked really, really bizarre,” he says. “I took a picture of Jack Black that we shot of him crying, and I pasted it on a baby’s body. Then we played with different sizes for the head.” Somewhere, tucked away on a nondescript external hard drive, are versions of Pre-Birth Animatronic Jack Black Baby in which Jack Black’s bearded head matches the size of the baby body. That one-for-one illustration was not alarming enough, apparently. In the end, artists needed to enlarge Black’s head to normal adult size, and attach the noggin to a tiny baby body, for the concept to achieve Morot and Roth’s preferred level of shocking.

“I was really surprised that Eli was able to sell that to the studio, to be honest.”

After taking a cast of the real Jack Black’s head, Morot, a modern Prometheus, sculpted his man-baby out of clay so as to match the proportions of the Photoshop design. There were tweaks along the way to ensure that Animatronic Jack Black Baby would keep impressionable souls of all ages up at night.

“I purposely sculpted the eyes a bit larger than what I had done in Photoshop, just to give it a bit of that baby essence back into the full-size head,” Morot says. To achieve maximum “baby essence,” the makeup artist referenced another pair of haunting screen eyes: Puss ‘n Boots from the Shrek movies.

Morot is not without regrets. The designer’s team built two Animatronic Jack Black Baby models for the House shoot: a static puppet that Owen Vaccaro could hold in his arms, and a more articulate version that could lay on its back, giggle, cry, and send any viewer directly into therapy. Morot wishes there were a version that were even more mobile; on set, he and Roth saw potential for a version that could crawl on all fours and really terrorize our lives. I assured Morot that the versions he created were extremely effective.

The designer says Animatronic Jack Black Baby was among his most difficult creations. Unlike hordes of extraterrestrials or demon-possessed human husks, a general viewer’s eye would be discerning when it came to a giant-headed, bearded baby, and the goal, however grotesque, was realism.

“If you’re doing a Jack Black baby, the head needs to be perfect, because everybody knows what Jack Black looks like,” he says. “The body of the baby needs to be perfect and must move in as real of a manner as possible, because everybody has seen babies. The second that you have some sort of weird clunky movement that might work for a creature there, it will not for the baby. It must be perfect.”

When I wake up in a cold sweat at two in the morning after suffering a flashback to Animatronic Jack Black Baby, I’m sure “perfect” will be the word I use, too.