Danger by Chocolate

"The Christmasy, chocolatey, vaporeon of Ghirardelli X decided to get some early treats, munching on a lot sweet, chocolatey treats left by anonymous being. After finishing the last one, a low hiss slowly began, only to have it grow louder and louder. Finding the source coming from her belly, she slowly began to get bigger, rounder, and lighter. It turns out those treats had some helium pods stuffed inside that were chewy like a filling, yet still effective once swallowed. Looks like those treats became a trick for this sweet flavored Pokemon."

Information Helpers: dracokid400 and IceandFireGuy