Warning: spoilers for The Substance.

The Substance sees Demi Moore and Margaret Qualley playing the same person but different versions of her, and it was key to the story that they looked similar but different at the same time. Written and directed by Coralie Fargeat, The Substance is a satirical body horror movie that quickly earned a spot among the best horror movies of 2024. The Substance received acclaim from critics during its festival run and release, quickly earning a “fresh” certificate on Rotten Tomatoes and successfully reviving Demi Moore’s career.

The Substance follows Elisabeth Sparkle (Moore), the host of a popular TV aerobics show who, on her 50th birthday, is fired. Later that day, she gets in a car accident and a nurse gives her information about a black market serum called “The Substance”. This is a cell-replicating serum that temporarily creates a younger and better version of the subject it’s injected into – however, the subject has to follow the instructions at all times, or horrifying consequences are unleashed. Elisabeth’s younger version goes by the name of Sue (Qualley), but despite being the same person, Sue looks different from Elisabeth.

Sue & Elisabeth Look Different Because Sue Is A Better Version

The Substance Is All About Creating A Better Version Of The Subject

The point of “The Substance” is to create a younger and better version of the subject – the problem is that the near “perfection” of the other selves can lead to them wanting to live their own life without the matrix. The subject who actives the process of the Substance is the matrix, and the double created by the serum is the other self. The other self needs the matrix to survive as it has to extract a “stabilizer” liquid from their back, but they have to switch bodies every seven days without exception.

Sue, as the younger and better version of Elisabeth, takes over her career, reviving it and doing everything better than she does.

This week-long rest also allows the matrix to recover and create more stabilizer liquid for the other self. However, Sue, as the younger and better version of Elisabeth, takes over her career, reviving it and doing everything better than she does, leading her to break the rules and use Elisabeth merely as a source of stabilizer serum, completely forgetting that she’s a living person who also has a life. The creators of the Substance make sure that their subjects don’t forget they and their duplicates are the same person, even if they don’t look alike.

The Substance shows some photos of younger Elisabeth in the hallways of the studio, as there were big posters of her younger years as a host of her aerobics show. These photos are of a young Demi Moore, and Qualley clearly doesn’t look like her – but that’s the point. The Substance makes a younger, better, and “more beautiful” version of the subject, so Sue can’t look like a young Elisabeth because, even though they are one, they are still different.

Sue & Elisabeth's Appearances Still Share Some Similarities

Sue & Elisabeth Are One, After All

The starter pack that Elisabeth receives from the creators of the Substance make sure to establish that, even though they are separate bodies, Elisabeth and her other self are one. In one of the many graphic scenes in The Substance, Sue comes out of Elisabeth’s back, and when she checks her young and “better” body out in the mirror, she finds the same birthmark Elisabeth has, though in a different part of her body. Sue is as athletic (or more) as Elisabeth and does have some physical similarities to Elisabeth though not enough to make anyone think they could be related.

Sue and Elisabeth have to have some physical similarities though not obvious ones as, at the end of the day, they are one and come from the same body. However, they are different consciousness, and it eventually becomes clear that Sue is more of a shell as she doesn’t really have a soul, and only cares for her own reputation and fame even if that means almost killing Elisabeth – so, in that sense, they are very different.

The Substance Making Sue Look Like A Young Demi Moore Would've Been More Challenging

The Substance Would Have Faced Major Problems (& Potential Controversies)

Making Sue look like a young Demi Moore would have been a lot more challenging than it might seem. To achieve that, The Substance would have had to use the controversial de-aging technology and more CGI that would have increased the movie’s budget, which can sometimes bring other production and post-production challenges. Digitally de-aging actors has been a controversial practice in recent years, as they often don’t look natural at all (as happened in The Irishman) and it ends up being more expensive than casting a younger, physically similar actor.

The Substance had a $17.5 million budget.

In addition to the production challenges that would have come with de-aging Demi Moore and having her play Sue, this wouldn’t have served the story. Sue becomes a big star because, while she’s similar to Elisabeth, she’s also very different: she’s younger, more beautiful, and fits exactly with the idea that Harvey (Dennis Quaid) and company had for Elisabeth’s replacement.

Even if Harvey hadn’t been Elisabeth’s producer years before, everyone knows what she looked like when she was young (because she was very famous and because of the framed posters at the studio), and it would have been very obvious that they were looking at a young Elisabeth. This would have given the idea that the Substance creates a younger but exact copy of the subject, instead of an improved version that can do what the matrix can’t.

Sue & Elisabeth Looking Different Is Important To The Substance's Themes

Sue & Elisabeth Had To Be Different & Similar At The Same Time

The themes at the core of The Substance are beauty standards, social pressure, aging, self-loathing, body autonomy, and the role of women in society. Sue not looking like Elisabeth when she was young creates a separation between them despite being the same person, and seeing Sue’s success further sinks Elisabeth into self-loathing – perhaps, if Sue looked like her, Elisabeth would feel more connected to Sue and her success, but instead, she’s looking at her improved version that doesn’t quite look like her.

The Substance addresses the idea of younger and more beautiful women having more value than older women.

Elisabeth ends up being tortured by Sue’s beauty and the success that comes with it, which, to her, was taken away from her as she aged, and Harvey got rid of her as if she had no value. The Substance addresses the idea of younger and more beautiful women having more value than older women, and Elisabeth, instead of enjoying the success of her other self, finds out that activating the Substance was the worst mistake she could have made. There’s a lot to unpack in The Substance, and Sue and Elisabeth looking similar but different is key to the story and its themes.