Now, this company made every White Walker, every limb,

every dead body since season four on "Game of Thrones."

We've been allowed to come into their top-secret studio,

but spoiler alert:

If you haven't seen some of the most recent episodes,

you might want to look away now.

BGFX is run by Emmy winners Sarah and Barrie Gower,

who've worked in the industry for over 20 years,

creating prosthetics for

"Life of Pi," "My Cousin Rachel," and "A Cure for Wellness."

I was working for various other prosthetics designers,

and I was doing little projects for makeup designers,

and I was doing things out

of a small studio at home in our back garden.

I was making bits and pieces, then we had a call

and went for the interview for "Game of Thrones,"

and that's where it sort of kicked off for us really.

Ju: Although we first see the Night King in season four

in Bran's vision, it's not until "The Door" in season six

that we see this version performed by actor Vladimir Furdik.

The whole process of making a head like this

is probably about, maybe three weeks.

We had a head cast in plaster of paris, and then we would

sculpt the whole makeup as one in like a plasticine.

We would make molds with fiberglass and epoxy resin,

and then we would cast the silicone appliances from them,

so it'll be like basically a big jigsaw piece

of various bits and pieces.

Every day that the actor films,

he needs a brand-new set of appliances.

Ju: This makeup weighs about 2 to 3 kilos

and takes four hours to apply.

But the Night King was originally planned

to look a little different.

We first sculpted a whole chest piece,

which came down here,

because I don't think the costume had been decided on at the

time as well, and at one point, he was going to be topless.

So it would've been an awful lot of work probably,

doing all the body artwork.

Ju: One of the most

recognizable characters is giant Wun Wun.

Actors who play the giants wear silicone appliances

while standing in front of a green screen.

And it's platinum-based silicone, which I think

was originally created for the medical industry.

When you get it in its raw state,

it's completely translucent. It's water-clear,

and then we pigment it to whatever tone we need.

So the softer the piece,

the easier it moves on the skin, basically.

But what's it like to wear one of these things?

That's like putting your hand inside of a plate of jelly.

Barrie: All the pieces are really cold,

so putting it on is a bit of a shock,

but everything warms up to the skin during the day.

How do you take off something like this? OK.

If you, there we go.

Ju: It's not just White Walkers, Stone Men, and giants

who need silicone masks. The process is also used on

fat suits, double chins, and chubby hands.

The show is filled with various wounds and infections, like

Jorah Mormont's greyscale.

Remember this scene in season seven where

Samwell Tarly removes all the oozing scales one by one?

It was effectively a lot of the same makeup,

but we had a slightly different chest piece,

which had an underlayer of raw skin,

and then we had a patch, which was preapplied over the top,

but that was all, had this sort of integrated blood tubing,

sort of led out the bottom of his piece

and down his costume, and there was myself and Paul Spiteri

behind him with just blood tubes and pumps,

and it was kind of on action.

Literally as they were peeling it away,

we had all this kind of methylcellulose slime.

Cut to me and Paul behind him just pumping all this

stuff coming out of him on cue.

Ju: Turns out the team used another

popular TV show for inspiration.

We're all big fans of "The Walking Dead" here.

We're always sort of scouring online,

looking at what they've been up to and what they're doing.

But for us, it was very important that

we want to do something quite different as well.

Turns out, there's a scale for how dead a wight looks.

Well, we have super fresh wights,

which came from Jane Walker's makeup department,

and they are extras which she just face makeup

and what have you, paled down,

and they pull out bone structure and a little bit of blood,

and then our fresh wights have small cheekbones appliances

where we can sink the eyes back a bit,

and we say they're about 6-months-old dead.

And then we have sort of mid-decomposed,

which are heavier pieces.

Top tip if you're using fake blood on somebody,

don't use a wet wipe to wipe it off

'cause you'll stain them orange.

Ju: Next time you're watching, keep an eye on the wights.

This is a cast of Michael Byrch,

who has played various roles in, wait for it, 12 episodes,

including that wight that jumps out of the crate

towards Cersei in season seven.

He's played so many parts.

He's been killed off so many times.

Ju: For battle sequences such as Battle of the Bastards,

real-life extras and horses

are mixed in with loose, fake limbs.

It's also these limbs that are pinned to the wall

in a season eight, episode one scene with Lord Ned Umber.

The life expectancy of these, if you make a load of props

for a sequence, it's rare you'll get them back

and they'll be in a decent condition

because they're usually covered in so much blood

and mud, and they're trampled on.

That's like my arm hair.

That's just human hair.

What is this made out of?

That's human hair.

Oh!

So we punch full heads of hair. We do eyebrows, eyelashes,

and it is actually natural hair, which is sold,

and we buy it in long lengths,

and then the guys actually precurl it

around small lengths of doweling.

An arm with that amount of hair on

would probably take a day to punch.

Ju: There are also entire trays of fake wounds.

We have the frozen-lake sequence in season seven.

Sixty to 100 wights on a day,

and just usually the nature of just how nuts

the filming process is, and how crazy the battles are,

we rarely had continuity days where we had to make sure

this guy looked identical each day

because he was often going to be seen,

so we were able to just make things up as we went

from day to day.

Ju: It's incredibly light and...

Barrie: It's a bit like jellyfish, isn't it?

Ju: Yeah, it's just like holding a jellyfish.

So what about all of those dead bodies we see?

They're made through a process called lifecasting.

So we'll start with capturing a former of the actor's

head or body, and we'll use a silicone lifecasting material

and a plaster bandage, so if you see people with casts

on their arms with the plaster bandage,

we use that as an outer shell,

and then effectively we have a mold of their head

which we can then pour in plaster of paris

to get a positive copy of the head.

These are all our, sort of our rogue's gallery of

"Game of Thrones," sort of, over the years.

Ju: Is that Joffrey?

'Cause obviously, he starts bleeding out of his eyes

and goes the color of radish.

So that was a bit of a collaboration between

Jane Walker and her team doing his makeup on the day,

and then it was visual FX as well.

They did quite a lot in post,

sort of making his eyes a little bit off.

Ju: We should probably qualify that the Arya head

was made for her Walder Frey mask,

and the Hound came here for his makeup tests.

But which adult-sized heads are underneath these bin bags?

We're not allowed to see them yet.

Aging is also a process that is used for various characters.

Remember that "oh, my God" moment when Melisandre takes off

her necklace in the season six premiere?

We used a lot of reference, I mean, old-age makeup

is something quite common in the prosthetics sort of world,

so we've got so many books and books,

so many files we've downloaded of elderly skin and textures

and what have you.

We did a very exaggerated kind of sculpture,

and it was accentuating the nose, all of the bone structure

and what have you, and then we had to thin her hair,

so she had a complete silicone bald cap,

and then she had a double,

who, really sweet, elderly lady,

I think her name was Sheila,

and we shot performance

with her as well

walking from the bed.

We shot her first, and then Carice matched her movements

as well, and visual FX kind of tied the two together.

Ju: That's all we have time for.

Our favorite bit?

Probably the realistic limbs made with human hair.

We won't be forgetting that anytime soon.