I love watching the series of animations created by Simon Tofield: Simon's Cat. I can tell that he's actually been studying a cat's behaviour, because of the way the character moves. I also find it entertaining and cute to watch as he exaggerates parts of the story and animation to make it funnier and the audience can relate to it in some way or another!
I find it interesting that something so simply made - just black outlines with the same, motionless background - can work so smoothly as an animated piece.
He even gave several tutorials on how to draw his characters!: