I'm making the Mickey Mouse cake from cake central with buttercream icing. When I place the cake head and ears on the sheet cake to build my Mickey Mouse do I crumb coat or ice the round cake head and cake ears before I place it on the sheet cake? Or do I put the mouse cake head and ears on the iced sheet cake with out icing  and then ice it? 

kinda depends -- i would tend to ice after placing it to contain the messiness -- but sometimes the design makes it difficult to reach -- for example if you were doing a number cake and you were icing the inside curves of the number 5 or something -- but a typical head and ears -- i'd probably ice after placement -- but like if the cake was real crumb-y i might ice before placing --

but there's no wrong way-- forge ahead and you'll develop your own methods and reasons for your methods--

best to you