Whole collection of Walt Stanchfield (Drawn to Life) is preaching on making each single frame/drawing “living”. If that achieved, chances of the sequence of frames being live is just a matter of some animation techniques.
For a moment just visualise a situation. You enter a waiting area (outside a science lab lets say). You see two persons sitting, one on left and other on right. The person on left actually is a dead body, but some technical arrangements (as an experiment) have been made so that a controlling person in other room is able to move all its limbs using some invisible rig and is also able to move its face skin. The person on the right is a real living person.
Now you enter the room. You see on your left. And that “person” moves with all its body, waves hand, a smile is pulled on the face to connect to you. Just visualise how much you will get connected to that.
Then you turn right. And there is a real person sitting. He just glances towards you, with a smile greets you, just a slight shake of his head. You immediately connect to him, become aware of him, respond back, empathise with him. You may go and sit with him and start a talk or enquire something. Because you know he is living, without much movement. And you didn’t connect to the first one, because you know that is not living even with so much of movement
This is the reality of good and bad animation. Animation is just meant to make a character “living” so the audience connect to him, may empathise with him.
I see lots of animations by students who have not actually learnt animation. There is so much of movement and no life.
Just look at these frames here. Don’t you feel that the character is living just by looking at a single frame. You feel the emotions inside the character, impulse behind each gesture, a living heart in each one.
You can find many examples where even after watching the character moving a lot, a lot for 1 minute, you are sure that he is not living, its a deadbody.
Just take care that we are animating and not moving dead bodies!!