I don't remember where I saw the Barbie crepe paper, but they probably have different licensed character crepe papers in the birthday party section of any party store.

You can imagine making a bat shape instead of a heart and adding Batman streamers, and it wouldn't even be that hard to make a spider web at the top with Spider-Man streamers coming down.  This is a simple, versatile design.

The Barbie streamers were just taped onto the botton of the heart before it was decorated.  The "flower garden" in the middle of the heart deserves a bit of explanation, though, because it's a useful decorating technique.

The light pink crepe paper that covers most of the piñata was snipped in the traditional way, but I wanted something else to break up the monotony of all that pink.  I came up with what I call the "floral technique" of decorating with crepe paper.  My usual method of snipping crepe paper leaves downward-hanging flaps that can be brushed upward to bring the piñata to life.  In the floral technique, the crepe paper sticks straight out from the side of the piñata, giving it a different look and texture.  The center of the piñata was intended to look like a bunch of roses.  The purple and white flowers around the dark pink area use the floral technique for the purple centers. (The white "petals" are just squares of crepe paper.)

A further description of the floral technique and step-by-step instructions for how to do it are available on the Crepe Paper page.