Stack the 3 chocolate cakes on top of one another. Spread a small amount of white icing between each cake to hold them together.
Cut off 1/3 of the entire cake with the cake knife. Start by cutting into the middle of the top layer at a hard slant into the second layer. End the slope at the edge of the third layer. Remove piece. This will be the back of the frog's head.
Cover all three cakes with white icing. Smooth over the whole cake with the spatula.
Fill a large open tip icing bag with white icing. Squeeze out the icing to form legs and arms that flow parallel from the top of the curve of the cake to the bottom of the cake. Position the arms on either side of the cake adjacent to the slant. Position the legs side by side on the front curve of the cake.
Swirl white icing slowly out of the icing bag to make hands and feet. Position them directly off of the legs and arms at the bottom of the cake. They should stick out from the legs and arms and lay flat on the surface your cake is sitting on.
Fill your icing air-brusher with green icing and spray the entire cake.
Create big white eyes by squeezing round circles of white icing from the icing bag. Make sure the eyes are on the top of the cake on the edge of the slant. The top surface of the cake is the frogs face.
Make a smile with black icing along the curve of the top of the cake. Pupils and nails are also done with black icing. Create a tongue on the frog with red icing. Be artistic.