These are days when they try and tape the Parade, sometimes with celebrities. It can get very very crowded on main street and by the castle, there's also more tv equipment around than you'd think. The parades and shows tend to get paused, stopped, restarted over and over until they have their footage.
In short, probably not the best time for a normal magic kingdom experience but fun if you want to see how the filming works.
Although not official, it seems like the taping dates will be november 29th, December 6th