In advance, tint 2 in. ball of fondant green. Roll out and cut head using bell cutter; let dry on board covered with cornstarch for several hours.
For hands, slightly flatten a small ball of green fondant and use craft knife to make right and left hand shapes, making cuts for fingers and thumb.
Shape fingers and palms, trimming where necessary. Reserve remaining green fondant. Prepare mini cake for rolled fondant by lightly icing with buttercream.
Position cake on foil-covered board. Roll out fondant and drape over cake, making folds for pleats in gown. Trim as needed to make flush with bottom of cake.
For arms, cut two dowel rods to 4 in. long. Wrap a 2 in. area in center of rods thickly with fondant, leaving 1 in. unwrapped at ends. Dampen one end of fondant sleeve and insert dowel rod in cake; carefully join fondant sleeve with body.
Attach hands to ends of dowel rods with icing. Pipe tip 3 dot eyes; add tip 2 dot pupils. Pipe in mouth and outline eyebrows with tip 2. Add tip 3 wavy lines for hair.
Roll a small ball of green fondant for nose and attach to face with a damp brush. Attach head to 5 in. dowel rod with icing. Insert into top of cake.