The most important Potterverse magical spell in Fantastic Beasts and Where to Find Them is easily the Undetectable Extension Charm. Without it, there’s no way for all the wonderful magical creatures could fit inside of Newt Scamander’s bigger-on-the-inside suitcase. Though it was glimpsed just a few times in the original Harry Potter books, this spell really defines the new movie.

The keywords “Capacious extremis!” translate loosely to “capacity and spacious,” which is accurate enough. The spell allows the wizard or witch to alter small enclosures — like bags — by creating all sorts of extra invisible space within them. Essentially, the Undetectable Extension Charm is a more explicable version of Mary Poppins’s endless carpet bag while simultaneously being a more whimsical, less science fiction-y iteration of the impossibly huge phone box from Doctor Who: the famed TARDIS.

If a fan of Doctor Who had never heard of Harry Potter, they might feel like Fantastic Beasts was more than just borrowing from the time-traveling hero and his box of endless rooms. Because the bowtie and dashing coat of Eddie Redmayne’s Newt Scamander are more than a little reminiscent of Matt Smith’s turn as the titular Time Lord of Doctor Who, when you add in Newt’s TARDIS-like suitcase, the whole image of Newt almost reads as well-intended plagiarism.

Wait, which one of us has a bowtie AND a thing that is bigger-on-the-inside?
Wait, which one of us has a bowtie AND a thing that is bigger-on-the-inside?

Still, if the Potterverse is borrowing from Doctor Who (or Marry Poppins) it’s been happening for a long time. The flying car which Harry and Ron commandeer in the Harry Potter and the Chamber of Secrets sported the Undetectable Extension Charm, which allowed the car to seat entire Weasley brood. Hermoine Granger also used the charm on her handbag, mostly so she, Harry, and Ron could store all of their supplies during their quest in Harry Potter and the Deathly Hallows to destroy Voldemort’s various Horcruxes. But Newt’s suitcase in Fantastic Beasts is the most extensive version of the charm the Potterverse has portrayed to date. It’s more sophisticated than a car with extra seats or even a bag with extra room. Newt’s suitcase contains entire habitats: a snowscape, a desert landscape, a forest, etc. Each terrain is seemingly separated only by a simple tent-flap.

How does Newt pull this off? Which in-canon Potterverse spell is he using to create these environments? Presumably, the creation of the myriad environments could just be part of casting the Undetectable Extension Charm, but this seems like heavy-duty magic. Hermoine’s bag probably didn’t require anything other than extra space, whereas Newt’s case is tricked-out with all sorts of foliage, water, and, most obviously, oxygen. If he weren’t already working for the Ministry of Magic, Newt could probably help the Muggles of the 20th century design some spaceships.

This forest exists in the suitcase.
This forest exists in the suitcase.

In terms of its scope, Newt’s suitcase is totally unprecedented in the Potterverse, even though the spell to create it was used before. The fact that Newt Scamander is able to maintain the existence of several unique worlds inside of his suitcase seems to indicate his magical abilities are pretty much off-the-scale. But the real question is whether Newt’s giant suitcase triggered magical laws to be passed in order to prevent another version of his case from existing in the future.

According to Pottermore, because the spell can obviously lead to abuse, “the Ministry of Magic has therefore laid down a strict rule that capacity-enhancement is not for private use, but only for the production of objects (such as school trunks and family tents), which have been individually approved for manufacture by the relevant Ministry Department.” So now we’re left wondering whether this rule existed before Newt’s adventures with the case in 1926 … or because of them?

In Fantastic Beasts and Where to Find Them, Newt’s case is briefly “impounded” by the American wizards who arrest him, suggesting that just the existence of his suitcase might be usurping the magical laws of 1926, at least in America. Newt is obviously guilty of transporting “illegal” magical animals, but the way in which he’s transporting them is probably just as illegal too. Because, if you think about it, using the Undetectable Extension Charm on this scale is a total game changer in the Harry Potter universe. Whole armies of Death Eaters could hide in suitcases, or, even thimbles. The various animals might be deemed “dangerous’ by various magical authorities, but the means by which Scamander cares for them are just as powerful.

In Lev Grossman’s novel — The Magician’s Land — Quentin Coldwater is preoccupied with conjuring an entirely new dimension basically from scratch. In the magical-world of The Magicians, this is treated as a huge accomplishment. But for Newt Scamander, something similar is created off-screen, and is pretty much no big deal. And though the wonderful creatures in Newt’s suitcase are perhaps the highlights of the films’s story, the suitcase is in many ways the real star. Because if Newt had the power to use the Undetectable Extension Charm to create this suitcase, who’s to say he doesn’t have a few spares.

Fantastic Beasts and Where to Find Them is out in wide release now.

Photos via Inverse and EW, Warner Bros., warner bros

Ryan Britt is a staff writer for Inverse. He is the author of the essay collection Luke Skywalker Can't Read and Other Geeky Truths (Plume/Penguin Random House 2015). His writing has also appeared in the New York Times, VICE, The Morning News, The Awl, Clarkesworld, BN Sci-Fi/Fantasy, Tor.com, and elsewhere. He lives in New York City.