My 3 y.o. drew on my LCD TV with a candle, the same applies for crayon (supposedly pencil and magic marker as well). I used a clean white eraser and baby wipes, gently rubbing/wiping; going back and forth between these as necessary. The screen dried slightly streaky, however that is easily fixed with a damp cloth where as wax is not.
http://en.wikipedia.org/wiki/MEGA_Brands_America,_Inc. Ruining your childhood dreams since 1923.