Your latest role is Queen of the Cuttlefish, in The Pout-Pout Fish; if you could be a fish for a day, which one would it be and why?

The blue groper at Clovelly beach – because it’s like an institution, and people go there to see it. I just think it’s cool that there’s a local fish that people actually go and see and talk about – it’s a special fish.

What film do you always return to, and why?

The 1942 Ernst Lubitsch film To Be Or Not To Be. I love this film. When I was growing up, it used to come on the ABC every now and again, and one time I videotaped it. I just thought it was so funny. It’s Carole Lombard and Jack Benny. Recently, they were playing it at the Ritz [cinema in Randwick], and it turned out that it was also the favourite film of a friend of mine, and so we went and just laughed and laughed and laughed. It’s such a great piece of comedy and all the actors in it are fantastic. Mel Brooks remade it in the 1980s – that wasn’t successful. But the original film is a brilliant comedy, to be watched regularly.

What’s the best lesson you learned from someone you’ve worked with?

I was doing A Doll’s House years ago with Pete [Peter O’Brien] – my husband now, but at the time we were not a couple. We were playing opposite each other and on opening night I tripped up – I jumped ahead a few lines in the script. I didn’t know what I’d done [but] I suddenly realised something wasn’t right. I remember looking at him, and he completely saved me in the situation, and then [the scene] took off again and went really, really well. But I think what I learned in that moment was, firstly, always trust the people you’re working with. If you don’t know where you are, if you turn around and look at the people you’re with, you will find where you’re meant to be in some way. It’s such a communal thing, acting on stage. And [secondly] just to have a sense of fun about it. Sometimes when something goes wrong, things actually spark off in a really great direction if you’re really present in that moment. It can be a gift when things go absolutely the wrong way.

What’s been your most memorable interaction with a fan?

It’s not just one particular interaction [but] when I meet fans of Lord of the Rings, particularly women, I hear a lot of stories about what Eowyn meant to them when they were growing up … things that had happened in their lives and how much that character meant to them and was some kind of help to them in those times.

What do you get asked about the most by Lord of the Rings fans?

The most specific question is always about the stew [that Eowyn serves Aragorn in a scene in the extended cut of The Two Towers]. “Was the stew really that bad?” It’s become such a joke, the whole thing about the stew, and everyone wants to know what was in the stew, and how was it made, and do you think she’s a better cook now, or do you think she really is a bad cook? People are, I think, obsessed with the humour of that situation. And I go into great detail describing the [ingredients] that made up the stew – because I remember what they did; like they even put bits of red cotton to make it look like bits of veins in the meat. They went to great detail to make it look as bad as possible.

What’s been your most cringeworthy celebrity encounter?

I was at a pilates class [in London] and there was a woman lying down doing pilates, and the teacher said to me: “Oh, Miranda, this is Miranda.” And I made some joke about, “oh, are you a journalist?” Because it’s an unusual name and most of the time when someone’s a Miranda, they’re a journalist. I wasn’t really seeing who it was. And when she got up, it was Miranda Richardson. Then I didn’t know what to say. I still had to stay and do my class, and I felt so embarrassed. I wanted to say: “Oh my gosh, I do know who you are!” I think she’s so fabulous and I was just too starstruck to say anything.

It’s been confidently claimed in several articles that you were named after Prospero’s daughter in Shakespeare’s The Tempest, and yet I’ve read you saying otherwise – can you settle the matter once and for all?

Yes – I was named after the Sydney suburb. Mum heard on the radio that they were opening a shopping centre at Miranda, and she thought that sounded like a nice name.

What’s the most chaotic thing that’s ever happened on set?

When I was working in Brazil [on 2013’s Reaching for the Moon] that was the most chaotic set I’ve ever worked on, and yet the film turned out incredibly well. But they just work in such a different way. The sense of time there is really different. In Australia, you normally have a call sheet, and you have to be on set by a certain time. [But] this was sort of open ended – you come on set whenever you happen to be ready. It was a really different way of working for me. The elements were all coming together at the very last minute, and sometimes they wouldn’t know where they were shooting the next day [or] how we were going to do it. And then you’d be in the middle of the scene and be like, “What was that noise that just interrupted the scene? Oh, it’s the producer popping open some champagne [on set], because he’s making a party.” It turned out great, but wow, it’s a really different style of film-making.

What are you secretly good at?

I’ve always been good with numbers. I memorise numbers easier than I memorise words a lot of the time, I’ve just got that kind of a brain. So I think if I hadn’t ended up in acting, I probably would have worked in something to do with numbers, like mathematics or accounting.

What’s the best piece of advice you have ever received?

When I was in high school, someone came to speak when we were graduating and they said, “don’t be afraid to fail” … which I think is the best piece of advice, because you learn so much more from failure than you learn from success. Success, you never really understand exactly how it happened. Failure, you learn so much more.

• The Pout-Pout Fish is in Australian cinemas now and in US cinemas on 20 March