Place the yoghurt in a bowl or container. Dip the banana halves in the coconut yoghurt, it will seem messy but don't panic, as soon as you roll them in the desiccated coconut everything firms up
Pop the coconut into a second small bowl or container, Roll the bananas in desiccated coconut and shake to remove any loose bits.
Add chocolate drops for the ghost eyes and mouth (I found small ones for the eyes and a large one for the mouth works best). A small blob of coconut yoghurt helps attach the chocolate drops.
Pop in the fridge for 30 mins or so before serving. You can leave them in the fridge for much longer, ie prep in the morning for an afternoon snack.
Notes
I found a blob of coconut yoghurt on the serving platter, prevented the boonanas face planting! Serving them on skewers also works (although the flat type are much better, the round bamboo ones mean the bananas just spin around and around)