Master make-up artist Rick Baker and Andy Serkis with the original 1933 King Kong miniature

Andy Serkis is "Kong".
The dots covering his face and body are used by video cameras to track his body movement and facial expressions, which are then animated into the movements and expressions of Kong.

Press to enter the Weta motion capture stage

Andy and Philippa Boyens in L.A. after long hours of ADR (voice recording) for Kong -- that's right, Andy also provided vocalizations for Kong: roars, growls, moans, sighs, breaths etc.

Andy Serkis, Naomi Watts and Peter Jackson on the set

Naomi Watts interviewed by Mike Sampson:

MS: How important was Andy Serkis to your performance?

NW: Oh, so important! I couldn't have done it without him.

MS: What was the interaction like?

NW: Well he was a character, like playing opposite any other man. He didn't have any words, but he had a huge amount of expression, be it physical or emotional. So I was just reacting to him the whole time. And in as truthful a way as possible.

MS: Was he in a monkey suit?

NW: He wasn't in a monkey suit with fur all over it. He was in a special suit that helped him move a sort of way. It was more about giving him the structure and posture that a primate has. He had teeth in, because that helped him, and then he also had a microphone and this thing they called the Kong-a-lizer. That did something to change the vibration or the frequency in his own voice. But every thing that you see on the screen, is Andy Serkis. I mean, yes there's been some magical stuff happened in the post production, special effects, but all the emotion all the movement, you know, how you see that ferocious face turn from that to sort of a smile come over him and a light in his eye, that's all Andy. And that's what I was reacting to, so that was – that's why it felt like a normal work space for me.

Read the full interview: JoBlo.com

Peter Jackson in Time Out:

"I thought it was important to be able to turn up and rehearse the scenes with Ann and Kong, and be able to talk to Kong. To have Kong (Andy Serkis) on set to talk to was a critically important part of the process. For Naomi, it gave her someone to act with.  Actors feed off each other; it's one of the key things of their craft; they use each other to generate performance. Virtually every single shot of Naomi looking at Kong, she's looking at Andy, she’s looking at his face and he's up on a cherry-picker or on a scaffold tower or somewhere. That was one part of the Andy Serkis situation. The other part was that Andy was the actor, the person, who studied gorillas more than anybody. He studied them more than I did. He went to Rwanda and lived up there for a couple of weeks. I did what I could but he did the real thing. If Andy said to me, 'that's not how a gorilla would behave Peter', I would obviously be paying attention." -- Peter Jackson interviewed by Dave Calhoun

First day testing Kong teeth and body
Wellington, NZ

Kong takes a well-deserved break

A gorilla's arms are longer than his legs, so Andy sometimes used extensions

Sound Department, Mocap Stage

Andy provided vocalizations for Kong throughout film production -- here in the ADR studio in Los Angeles

Voice of Kong in NY -- ADR studio, Los Angeles

Philippa Boyens and Andy Serkis on mocap stage