I have been to WDW MANY times and have heard about tours of the underground of the Magic Kingdom. Does anyone know about these? What are they called? How can I schedule one? Prices, etc. I think we might actually have the time this time to do one! 

You'll wear a headset too so you can hear everything your guide is saying. If you have an AP or DVC you can get a discount, 10-20% off. It changed so I'm not sure of exact amount. I can tell you it was worth the $46/each for us and my son loved it too! I wish we didn't do it just to do it again!