1. Trim the tops of all the cakes to make them level. Place a 9-inch cake on a serving platter and cover the top with vanilla frosting. Stack the other 9-inch cake on it and spread a thin layer of frosting on top. Refrigerate the cakes for at least 30 minutes. Prep the two 6-inch cakes in the same way.
2. Cover each chilled two-layer cake with vanilla frosting. Place the smaller cake, on the cardboard, on the larger cake. With the chocolate frosting, pipe a birthday message onto a large lollipop, then insert it into the top of the cake. Embellish the rest of the cake with smaller lollipops by inserting the sticks into the cake.