Oh pencil... you're so random!

I know it's not perfect... but I had to get this out of my system today!

The reason why the pencil (in real life) appears to wiggle:

Visual perception has as much to do with how your nervous system processes the light. Different parts of the retina process in more/less detail depending on where they are. Greatest attention is given to the centre of one's field of view, peripheral vision is processed with lower resolution.

So, if you focus on one part of the pencil to see it more clearly, the other parts of the pencil are perceived with an effective time lag, therefore looks bent.