"Xandra, with an 'X'."
That's how Sarah Paulson introduces herself in The Goldfinch, in cinemas now.
Adapted from the Pulitzer Prize-winning novel of the same name by Donna Tartt, it's the story of a young boy wracked with grief and riddled with guilt by his mother's death in an explosion at New York's Metropolitan Museum of Art.
In the aftermath of the disaster, Theo steals a small but priceless work of art and spends the next decade of his life atoning for that theft.
Paulson, 44, makes an entrance — because that is exactly what she does — about a third of the way through the movie.
Theo (Oakes Fegley), has just started getting comfortable living with his school friend under the watchful eye of Andy's perfectly-appointed mother Mrs Barbour (Nicole Kidman) when there she is: Xandra with an X, girlfriend of Theo's wastrel father Larry (Luke Wilson).
She arrives in Mrs Barber's chic Upper East Side salon in a pair of second-skin jeggings, open-toe stilettos and a furry gilet.
With poker-straight hair extensions, a set of French tip acrylics and an Anzac biscuit spray tan, Paulson is almost unrecognisable.
"I'll say," she says, laughing.
We're speaking at the Toronto International Film Festival, where the film has had its world premiere. Here, Paulson looks like Paulson — shaggy blond bob pulled back behind a thick black headband; clad in a horse-printed Miu Miu dress.
Which is to say she looks like the Golden Globe and Emmy award-winning star of The People vs O.J and Ocean's Eight.
And though she enjoyed dressing up in the Vegas glad rags of Xandra with an X — "I'm taking Xandra to the MGM Grand," Larry tells Theo at one point in the film, "for Thanksgiving dinner!" — Paulson says the costuming did give her pause.
"It was scary for me," she explains. "I haven't been in a bathing suit — I haven't worn a pair of shorts since I was, I don't know, probably 15. And there I was in really short … Well for me they were short. And a midriff top! And a bikini!"
Paulson is referring to a scene in the middle of the movie when Theo and his friend Boris (Stranger Things' Finn Wolfhard) see Xandra reclining by the pool. That, the actor says, was a difficult moment to film.
"I wear a wetsuit in my own swimming pool," Paulson jokes. "I'm not interested in that kind of thing. It was challenging."
But this, she adds, is exactly why she wants to take on transformative, shapeshifting roles like Xandra with an X in The Goldfinch. Paulson says she cancelled all her plans when the book was first released in 2013 to stay home and read it cover to cover.
Originally, The Goldfinch director John Crowley wasn't convinced on Paulson for the role, but she fought for it and was eventually cast alongside Wilson as the schemers who plot to "take the boy," as she puts it.
Fegley says that shooting with Paulson, Wilson and Wolfhard in Las Vegas was "a lot of fun". "The four of us were just joking around a lot on set, even when we weren't in the same scenes, we would just have so much fun," he tells news.com.au.
"We're a good time!" Paulson grins. "Larry and Xandra, we're a good time!"
Which, for a while, they are.
Theo's first few weeks in Vegas are a whirlwind of takeaway dinners and playtime with Xandra's pointedly-named dog Popper. Eventually, though, the relationship between Theo and his father and new stepmother take a shocking turn.
These are some of the most difficult scenes in the film to watch, and were challenging for Wilson and Paulson to shoot.
"You always worry," Wilson explains. "Those darker scenes, and not knowing Oakes personally. And then getting to know him while you're shooting and you learn that he has a great dad, and he loves his dog, and he has a nice little brother."
Wilson credits director Crowley with creating an atmosphere on set that was supporting and thoughtful, which "enabled us to focus on what we were trying to do and lean into that negative vibe," Wilson explains.
The challenge of a film like The Goldfinch is the thing, then, whether it's exploring darker subject matter of conquering a fear of itsy-bitsy, teeny-weeny bikinis.
"I do think that if we expect to grow at all as performers … I don't like to use the word artist, it makes me want to take a shower," Paulson says, shrugging.
"I will say, though, the moment they did tell me that I did get to have the part, I immediately thought about the bathing suit. Like, oh, sweet Jesus. There's no way to avoid it. But this woman thinks she looks great! And so, I had to kind of embrace it. But it wasn't easy for my brain."
The Goldfinch is in cinemas now