"One question repeatedly popped into my mind during “The Substance,” an outrageous and beyond bizarre horror movie that had its North American premiere Thursday night at the Toronto International Film Festival.

What’s wrong with these people?!

Our judgment begins with the damaged-to-deranged characters.

Elisabeth Sparkle, played to the hilt by Demi Moore (what’s wrong with her?!), is an Oscar winner turned fading fitness guru a la Suzanne Somers whose luxurious Hollywood home is plastered with giant portraits of her in her prime.

After Elisabeth is abruptly fired from her TV job, “Sparkle With Elizabeth,” the gutted actress learns of an underground drug called the Substance that promises to create a younger, sexier doppelgänger of a person. A certifiable California narcissist, Elisabeth signs right up.

This is when we start to wonder what’s wrong with the astronomically talented and created writer-director Coralie Fargeat, whose French nightmares this astounding film surely sprang from.

When Elisabeth injects the plutonium-green Substance, her back gorily splits open, and her nubile clone pops out like a xenomorph in “Alien.”

The one unbreakable rule, with gnarly consequences, is that the young counterpart can walk the earth for only seven days at a time — while Elisabeth basically hibernates — before they swap places again.

Almost immediately, Liz’s piggish former boss (Dennis Quaid at his funniest) casts the gorgeous clone, who names herself Sue, as his hot new workout show host of a program called “Pump It Up.”

Elisabeth awakens only to be taunted by billboards and posters of Sue, and develops a love-hate relationship with her popular counterpart.

Moore, at her most game and frequently unclothed, gives one of her best performances in years — going from It girl to Gollum in over two hours. Impeccable makeup and prosthetics help, but the true terror is created by her beneath the surface.

Qualley, by contrast, spends most of the film smiling and squatting — never boringly, mind you — but that shiny veneer conceals building resentment and darkness.

Opportunist Sue would rather not take a weeklong nap after seven days and goes to harmful extremes to stay awake. (Something is definitely wrong with her.)

That leads to a Grand-Guignol finale so weird, warped and funny that we sit in awe of the fact that investors actually said, “Sure, we’ll pay for that.”

As for the audience, something is wrong with us, too.

I enjoyed this ride of titillation, torment, insanity and exploitation to such a preposterous extent that I’ve considered signing up for online therapy to wrestle with it.

Perhaps that’s because, as jaw-droppingly odd as it is, “The Substance” is part of a grand, campy tradition. The movie is the hotter, younger offshoot of “Death Becomes Her” and, being set in a two-woman LA household stewing with envy, even “What Ever Happened to Baby Jane?”

By the end, it’s “Frankenstein” and “Young Frankenstein.”

Where Fargeat’s film distinguishes itself — and will send some viewers sprinting to the bathroom — is the amble body horror elements.

Hers is a provocative, gruesome, bloody and, for some, nauseating movie that will be hugely controversial when it hits theaters later this month.

Much like the title drug, it’s hard to broadly recommend it without listing off a host of side effects.

However, at the movies today, there is nothing wrong with unbound creativity, epic vision and some gonzo entertainment.

And, by the way, in its smart send-up of our youth-obsessed culture, there’s even a little substance, too."