Watching a 3D-model of a disembodied hand wiggle and flex is weirdly satisfying. Pixar animators developed a novel way to realistically animate flesh and muscle, and demonstrated their techniques using a skeleton hand, a very ripped torso, and various other spooky, disembodied parts.
The animators, Breannan Smith, Fernando de Goes, and Theodore Kim, call their approach "Stable Neo-Hookean Flesh Simulation." The neo-Hookean model is, from what I can gather from various scholarly articles and the incredibly complexWikipedia page on the subject, a combination of very intense algebraic equations that explain the mechanics of movement as it relates to volume. I could be wrong about this, don't send me emails. I'm just a fan of awesome-looking 3D slugs, rocks, and now, flesh.
Applying the neo-Hookean model to their animations results in movement without the cartoonish stretching and folding that happens when you manipulate objects in animation. We've come a long way since the GoldenEye 007 hand days.