Kids, this is a scenario where I'm not going to tell you to ask your parents. I'm just going to flat out tell you myself. There once was a time when you couldn't make any damn thing you wanted show up in a movie using a computer. You used to have to use practical FX...exclusively. And so when you wanted something that shouldn't ordinarily move around on its own--say, a skeleton with a sword or a Gorgon--you would need to take a model of said thing, take a picture, move it, then take another picture and so on with excruciatingly slowness. Eventually, you could piece together all the pictures with their very, very slight changes and play them at speed...and you get the illusion of movement. Stop motion.
The granddaddy of visual effects and the King of Stop Motion was Ray Harryhausen. From 1949 to 1981, if you dug a genre film that used stop motion...there was a pretty good chance Harryhausen was the man behind it. Exhibit A comes after the jump.
The list of his films is huge. And if you want to know why a lot of the new Clash of the Titans was shite...it's because it lacked the charm of the original, which featured a ton of Harryhausen creations. And now, Ray Harryhausen has died at age 92. Rob is correct in that we will never see Harryhausen's like again. Take a moment to reflect on how much of an impact he had on the careers of Lucas, Cameron, Jackson, Spielberg, Burton and scads of other filmmakers...and how we wouldn't have films like we do today if he hadn't have been there to blow our minds with what was possible at the time.
Once you're done reflecting, here's an additional vid of him interacting with the armature from Mighty Joe Young, his first film. Thanks for everything, Ray.