A nice example of a screen cast demo. No avatar, but the "teacher" does introduce himself. There is a nice tone to the demo with little superfluous stuff.
This site does a good job of showing what this application is about. The little "demo" at the top tells the story very well, as do the examples further down the page.
Another nice example of a training video, this one from Apple. I like how this demo shows people the process at the beginning during the intro, and then goes into greater detail.