Answer from Piñata Boy
The simplest piñatas, the kind you often see in stores, are flat on the front and back and a few inches thick. To make one like this, you would simply draw out a full-size picture of the piñata you want to make on a large piece of paper, then cut it out along the outside edge, and trace the perimeter twice onto a piece of thin corrugated cardboard. Cut out the two shapes from cardboard and you have the front and back of the piñata. The edge of the piñata is also made from thin cardboard. For the edge you will need a strip of cardboard that is as wide as you want your piñata to be, and long enough to go around the entire perimeter of the piñata. Most like you will need more than one piece to go all the way around.
I don’t normally make piñatas of this type, but if I did, I would attach the edge strip to the front using a line of hot glue, then put masking tape or papier mâché over the seam to help cement it in place. Then attach the back the same way, and decorate the front and back according to the unicorn image you have in mind. You’ll want to give the edge some kind of decoration to cover up the cardboard there as well, and don’t forget to install the hanging hook before you attach the back and close up the piñata.
If you make one this way, you’ll want to use the thinnest corrugated cardboard you can find — a piñata made from ordinary corrugated cardboard is almost indestructible. You can add a layer of papier mâché to the cardboard to help stiffen it up, but this will toughen the walls and even thin corrugated cardboard is usually pretty hard to break already.
If you want to make a three-dimensional unicorn piñata, then you’ll want to think in terms of building a hollow statue of a unicorn. A unicorn is basically made up of a body, four legs, a neck, and a head. You can use balloons for the body and head, and something like paper towel tubes or wrapping paper tubes for the legs. For the neck you might want to create a sort of cone shape using thin cardboard. To make a unicorn piñata this way, you would cover the head and body balloons in papier mâché, then use masking tape to assemble the pieces of the piñata, then cover the masking tape with papier mâché to cement it all together.
Structured piñatas like this often don’t come out quite as planned, but the nice thing about piñatas are that they are so forgiving. Piñatas are expected to be fun, so if your unicorn comes out a little lopsided, or the legs aren’t all the same length, or the head is too big or maybe it’s on a little crooked, that just adds a fun, cartoonish feel to it. I have had a lot of piñatas over the years take on a life of their own and end up being not quite what I had in mind, but that’s part of the fun. The details — in this case things like the eyes, ears, horn, hooves, and tail — are another place where you can add lots of quirky personality to the piñata.