How did Kong and Harryhausen's skeletons come to life?

With small jointed models, a great deal of patience and some clever tricks for putting them into real scenes. The pioneer was Willis O'Brien. For King Kong in 1933 his team built models about 14 to 18 inches tall, with metal armatures inside, padded with cotton, latex and rabbit fur. An armature is a metal skeleton that lets a model hold a pose. In stop motion, the animators move a model a tiny bit between individually photographed frames, so it seems to move when the frames are played back. The fur on the Kong models moved as the animators handled them, which became an unintentional feature of the character. Animation for the film took 55 weeks.

The models were small, but the actors were not, so the film had to bring them together. One method was rear-screen projection: a projector shows footage onto the back of a translucent screen behind an actor. For the scene where Kong fights a dinosaur, the animation was filmed first, and then Fay Wray sat in a fake tree for 22 hours, acting out her reaction while the battle was projected behind her.

A boy named Ray Harryhausen saw King Kong on its first release, and then many more times. O'Brien looked at his early models and told him to study graphic arts and sculpture. Harryhausen grew up to create Dynamation, which split live-action footage into a background and a foreground and animated a model between them, so the model looked sandwiched inside the real scene. His father machined the metal armatures for his models. In Jason and the Argonauts, a fight between three actors and seven living skeletons took over four months.