In advance: Make bunny head. Roll out fondant 1/4 in. thick and cut head using bunny cutter. Let dry overnight on cornstarch-dusted board. When dry, draw facial features and inside ears with FoodWriters.
Position cake on board, flat side down. Spatula ice cake using orange icing to create a banded carrot look, moving from left wheel side to right.
Combine Kelly Green and Leaf Green for green icing shade shown. For wheels, using tip 5 dots of icing, attach candy-coated chocolates to discs and discs to cake.
For bunny body, pipe tip 7 mound for chest, tip 5 mound for neck. Insert fondant head. Attach candy disc steering wheel with icing. Pipe tip 5 outline arms, attaching right arm to steering wheel. Add tip 18 pull-out star greenery.