Better red than dead

Sophie McBride (above) and Thomas Cameron had to do various exercises to develop the strong 'twinness' of their characters. Photo / Supplied by Disney

Sophie McBride and Thomas Cameron neither knew each other nor much about Maurice Gee's original story when they landed the role of the red-haired heroes Rachel and Theo in Under the Mountain.

They didn't have the required hair colour, either.

But in the year before filming and dye jobs, acting coach Miranda Harcourt had them doing exercises to build the strong "twinness" of their characters, which pulses though the storyline.

It dissolves, then swells into a bond so powerful that it is big enough to save the world.

Or Auckland, at least.

One of these exercises was "hug to connect".

"You hug for two minutes, completely quiet with relaxing music. Just hug," Cameron explains, sitting in a hotel suite above the city where Under the Mountain is set. Sitting next to Cameron as they face a day of interviews is McBride, fizzing with energy.

"It's a really bonding experience," McBride says of the mighty hug, giving an emphatic nod.

In the year since filming, McBride has moved to Wellington to do an arts degree, while Cameron has wrapped-up his last year at King's College; but it seems distance hasn't broken that camaraderie that Harcourt worked so hard to develop.

They are batting banter, clarifying each others' sentences, if not finishing them.

"We definitely do have a twin bond," McBride says.

"There was this one time Jonathan cooked a dinner at his house and I was thinking about saying something and then she goes, 'what did you say'? So yeah, there's something going on," adds Cameron.

The naturally brunette pair were both at school when they were thrown into King's crazy world being smeared with slime (KY Jelly) and chased by men in hideous prosthetics.

"At one point they poured lots of slime on to a tarpaulin and us two got to writhe around in it, because it was a slimy scene, we had to be all slimed up. But the novelty of it wears off pretty quickly; we got pretty cold," McBride says.

Screaming "more slime, more slime!" King would take the gunky mixture off the Weta Workshop people and smear it all over the actors' faces.

Cameron says it's kind of like the gore obsession in Black Sheep, only he has switched the blood with stuff that's clearly not human.

It might keep the film on a PG rating, but McBride is certain Under the Mountain is going to scare its young audience.

She insists Rachel's shrieks didn't just come out of good acting.

Those Weta workshopped characters were terrifying: "There was some genuine fear going on," she says.

Cameron says Oliver Driver, who plays Mr Wilberforce, is pretty scary himself - he's frighteningly tall.

Then again, they were sweating enough just being on the same set as some big time actors such as Sam Neill.

"We met Sam Neill and it was all oh, such a huge deal but he was so calm and modest and really generous, giving us tips and things," McBride says.

One of those was a little jingle that they sang every day to relax themselves.

It's called the ginga song and it goes like this:

"I'm a ginga, and you're a ginga too, so come on ginga, I want to ging with you ... " they sing then collapse into giggles.

Under the Mountain is not just about another Harry Potter and Hermione duo saving the world from fantasy monsters - or a Harry, Ron and Hermione trio if you count the cousin Ricky - nor is it one of those long-whispered-about legends of underground slug creatures told with special effects.

It's not even about bringing tourists to Auckland, though it probably will. And it's not just a film to celebrate the power of twins.

What the film really is about, according to McBride, is the power of red-headedness - or being ginga.

"It's all about the ginge pride, promoting ginge egos they need it."