A rubber ducky cake, whether for a baby shower or a first birthday party, would not be complete without realistic bubbles. You might design the cake to resemble a wash tub, place a rubber ducky centered on the top, and surround the duck with bubbles so it looks as though it's taking a bubble bath. Alternatively, add bubbles to accent the cake base. Buttercream frosting and basic cake decorating supplies are all you need to make the bubbles. Substitute vegetable shortening for the butter in the buttercream recipe so the frosting hardens and the bubbles won't soften at room temperature.

Insert a decorating tip coupler in a decorating bag and fill the bag with white buttercream frosting. A coupler makes it easy to switch out different decorating tips without needing a separate bag of frosting for each tip. Insert a large, round decorating tip and screw on the coupler cap to hold it in place.

Hold the decorating bag at a 90-degree angle with the cake surface, positioning the tip close to the cake without actually touching it. Squeeze the decorating bag with firm pressure to squeeze out the frosting. When the circle of frosting spreads out to the desired width for the largest bubbles, slowly lift the tip straight up away from the cake to form the icing into a ball. Stop squeezing the bag and lift it straight up from the ball to break off the icing stream.

Pipe several large bubble balls all over the cake to fill in the the majority of the rubber ducky tub scene.

Switch out the large tip for a medium, round decorating tip. Pipe medium-sized balls in the empty spaces between the large bubbles. The smaller tip works the same as the larger tip.

Switch to a small, round decorating tip and fill in the remaining empty spaces with small balls to resemble small bubbles. Additionally, pipe a few small bubbles on the larger bubbles to mimic the natural tendency for several bubbles to attach to each other.

Allow about 30 minutes for the bubbles to harden on the surface. Brush pearl dust on each bubble with a small paintbrush to give the bubbles a shiny surface that looks even more like real bubbles. Apply pearl dust sparingly because a little makes a big impact.