I've seen this video before it's great to see behind the scenes and let the average fan see how much work goes into this. I myself am an aspiring voice actor, though I am focusing more on Japanese anime and video games rather than American animation. I've posted these videos in the Anime usergroup but I would just like to share some of my amateur voice acting roles with you guys.
The recording is done a bit differently than with Family Guy, since they do the recordings first and then the animation. Whereas with Anime voice overs the animation already exists and you are tasked with matching the lip flaps and timing that already exist. American animations tend to have more distinct voices that don't have as large an emotional range while Anime tends to be very dramatic and calls for a good range of acting and emotions rather than a specific "voice" for a character.
It is pretty cool having 1 person doing the voice of multiple characters of a television show. Seems like a long and grueling process for some scenes though, having to do it over and over again to get it just right. Pretty cool none the less.