All you need to do is enter any common room on Poptropica and look for the balloon with the 7 on it. Pop it, and you'll get this prize!
We'll help you find this outfit in a couple ways. First, we'll be turning up the frequency of the 7 balloon, so you've got a greater chance to see it and win.
Second, we've also added a brand-new common room to PoptropiCon: Line Forms Here! Visit "The Facili-Tee" in the main Convention Center scene for our first new common room since Monster Carnival.
Enjoy!
BLACK WIDOW