In the fifth and final season of Stranger Things, Fisher takes over the role of Holly Wheeler - the younger sister of Mike and Nancy.
When she found out she'd been cast, back in 2023, the London-based actor was weary from a day shooting the family film Bookworm on a rainy Canterbury hillside.
"What had been a pretty exhausting day turned into one of the best days of my life," she tells RNZ's Saturday Morning.
Joining the cast of Stranger Things was "quite scary", Fisher says.
"You're putting quite a lot of yourself out into the world doing these performances, and you're not necessarily sure how the world is going to receive it, what they're going to think of it."
In earlier seasons, the character of Holly Wheeler (previously played by twins Anniston and Tinsley Price) was "on the sidelines" of the mysterious parallel dimension known as the Upside Down, she says.
This season, it will be explained to her.
"Holly really gets thrown in the thick of things… she really gets thrown in on the action. I am basically a walking spoiler, so I'm trying to tiptoe my way around this."
Fisher can say that developing a realistic mother-daughter connection with the "wonderful and incredibly talented" actor Cara Buono, who plays her mother Karen, came very easily.
"We spent about two days in a bathtub, just laughing our heads off and having so much fun."
Her previous experience with "screaming and crying" on the NZ-shot horror film Evil Dead Rise came in handy as Stranger Things creators Matt and Ross Duffer take a "real" approach to filming the show's supernatural scenes.
"Quite a lot of the effects are actually there while you're filming, which is quite useful to be able to have something you can react off of."
Acting is a unique thing that not many people get to experience, and Fisher feels lucky to be cast.
"I take what I do seriously, so it is just finding a real emotion, then expanding on it, and putting in your situation and in your character, and then it all sort of snowballs."
She was very nervous joining the cast of Stranger Things as most of them had worked together for almost a decade, but everyone was friendly and supportive.
"It was definitely a different dynamic, because for me, this is like the start of an amazing new adventure, and for them it's sort of like the end of ten years."
The table read of the Stranger Things finale was really lovely, really informal and at the end really emotional, Fisher says.
"We were just kind of sitting on sofas, all like wet with tears.
"It's ending, which is difficult, but the way the Duffers have ended it is just so perfect. It's so beautiful."
Fisher, who reckons she came out of the womb "singing and dancing and wanting to be on the spot in the spotlight", also has performing in her genes.
Her dad Toby, an actor-turned-lawyer who played a teenager with cancer in the 1993 film The Whole of the Moon, has been "a massive help".
Before working on Stranger Things, Fisher felt like she'd just "stumbled" onto a movie set and didn't quite belong - now that's changed.
"I feel like I am an actor, and I am here to stay, which is really exciting."
For now, though, the hard-working performer is taking a well-deserved break.
"Last year was fantastic and amazing, but it was also quite exhausting, so I've been taking a bit of a break, getting back to normality, but I'm really excited to see what the new year holds.
"I'm actually back in New Zealand at Christmas and New Year when [the Stranger Things finale] drops, because, yeah, I'm part Kiwi. I'm really excited to be there with everyone when the world gets to see how it all ends."
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