Most people associate notorious Wisconsin serial killer Ed Gein with the chainsaw-wielding, mass-murdering movie villain Leatherface — but it turns out a sweet 1949 cartoon character was the true inspiration behind the deranged fictional terror: Baby Huey.

The giant, naive duck, in a TV show of the same name, was an outcast among his fellow ducklings and hunted by a fox desperate to gobble him up.

Similarly, Leatherface was a big oaf with no friends and waddled around making animal noises. But in contrast to the animated duck, Leatherface and his two twisted brothers were the hunters, slaughtering humans in the most ghastly fashion in the 1974 horror classic, “The Texas Chainsaw Massacre.”

“He never became an adult. He was like Baby Huey. It’s kind of the way I envisioned him from the cartoons,” “Chainsaw” director Tobe Hooper revealed about his Leatherface character, originally played by actor Gunnar Hansen, who died last year at the age of 68.

Hooper spoke at length to The Post in a 90-minute interview, sharing secrets about “Chainsaw,” as the 42nd anniversary of the film’s Oct. 1 release approaches.

The 73-year-old filmmaker, who also directed “Poltergeist” and “Salem’s Lot,” mostly shed light on the back stories of “Chainsaw’s” killer clan — giving more depth to the fiends than what is actually shown on screen.

The homicidal family is composed of Leatherface, his two older brothers — known as The Hitchhiker and The Cook — and family patriarch Grandpa. (The characters weren’t given proper names in the film.)

Some of Hooper’s revelations include the inner workings of the brothers’ cannibal restaurant business, family members’ penchant for necrophilia and Leatherface’s motivation for hanging one of his victims from a meat hook.

Good times!

Over the years, “Chainsaw” — co-written by Hooper and Kim Henkel — has spawned four sequels and countless copycat films, but none of them measure up to Hooper’s masterpiece.

Renowned movie critic Rex Reed once called the film, “The scariest motion picture I have ever seen.”

He’s not alone.

Even Patrick Bateman in “American Psycho” was a big fan of the movie, using it as an exercise video and killing a prostitute with a chainsaw in the spirit of Leatherface.

“Chainsaw’s” plot follows Sally Hardesty and her wheelchair-bound brother, Franklin, as they take a road trip to check on their grandfather’s final resting place at a Texas cemetery amid news reports of grave robbing and vandalism there. Sally’s boyfriend, Jerry, her friend, Pam, and Pam’s boyfriend, Kirk, go along for the ride.

After the cemetery visit, they pick up The Hitchhiker while en route to the Hardestys’ old family homestead about 20 miles north of Austin.

The Hitchhiker cuts himself and slashes Franklin before getting booted from the van. Franklin suffers a nasty gash, but he lives— SPOILER ALERT! — at least temporarily.

The group pulls the van into a Gulf station to fill up the gas tank. They meet the strange proprietor, The Cook, who sells them barbecued meat. (Uh, oh.)

They eventually find their way to the brothers’ house of horrors, where most of the them meet their horrible demise at the hands of Leatherface.

It gets worse — with what Hooper calls the brothers’ “cannibalism for profit” business.

It’s heavily implied in the film, but Hooper explained that Leatherface was the butcher, clad in a chef’s apron. As the victims sporadically arrived at the home, Leatherface dragged them into the kitchen and sliced them up like a Sunday roast. He placed their body parts inside a freezer to preserve them while processing the “meat” of past victims and doling out the pieces to The Cook at the barbecue pit — who served it to paying customers.

In one terrifying scene, for example, Sally gets chased to the gas station by Leatherface and winds up at the barbecue pit waiting for The Cook to help her—ignorant that he’s a party to the mayhem. She looks inside the pit at the meat being roasted and suddenly realizes that something’s amiss.

“That’s her first clue of what’s really going on,” Hooper said.

Meanwhile, even if we don’t see it on screen, The Hitchhiker and The Cook are suspected necrophiliacs, Hooper said.

‘I called the MPAA and asked them, “How can I hang a girl on a meat hook and get an ‘R’ rating?” And they said you can’t.’ - Director Tobe Hooper

And the 110-year-old family patriarch, Grandpa, had a real taste for it as well at one time — with Grandma’s corpse.

“They were totally off the grid,” Hooper said. “They lived in their own microcosm. It seems unimaginable, but they were happy for the most part.”

Small comfort to victims like young Pam, who, before her own demise, was hung by a meat hook while Leatherface went to work on her boyfriend Kirk.

Why the meat hook? It wasn’t abject cruelty, Hooper said. It’s just that the hulking madman had no other spot for her.

“He needed a place to put her where she can’t get away,” Hooper explained.

Hooper was concerned that the disturbing scene would win him a dreaded “X” rating from the Motion Picture Association of America.

“That’s why I called the MPAA and asked them, ‘How can I hang a girl on a meat hook and get an ‘R’ rating?’” Hooper said. “And they said, ‘You can’t.’”

But Hooper promised not to make it too gory, which, in the end, got the MPAA off his back. “Chainsaw” was ultimately given an “R” rating and, as a result, was given wider distribution.

But back to more of Hooper’s revelations of the family’s inglorious, unfilmed back story:

The director surmised that Leatherface was on the path to becoming a mad butcher when the monster was still a child and that The Hitchhiker was the first to dress him up with a human flesh mask. Grandpa then did “something that kicked that starter switch,” and the family business was born.

“Something happened back there and the family ran with it. I’m not sure I want to know about it,” the director said.

Then there’s the frenzied finale, when Sally eludes a frustrated Leatherface, who’s been chasing her to a road with his trusty chainsaw.

Sally quickly jumps into the back of a pick-up truck that has stopped for her. As she’s whisked off to safety, Leatherface goes into a bizarre “war dance.” He pirouettes like a demented ballerina while swinging the whirring chainsaw in the middle of the road.

“This was just the last straw. That truly made it a bad day,” Hooper said. “The electricity between everyone and everything that was happening was so chaotic and outrageous and completely nuts.”

And the screen goes black.