Does anyone know what tip you would use to make a ghost with a piping bag? I've seen them made with marshmallow buttercream, but I'm not sure what tip and technique to use.

there is a picture of these ghosts on i am baker's blog at www.iammommy.typepad.com/i_am_baker

I dont have the big huge round tip I have been pining over yet, so I just cut the tip off the plastic pastry bag and went to town!