Garden Gnome and Doppelganger

Here's a strange idea I had recently. It's kind of been a spin on another idea I have a while ago. What if this kid finds a mummified fetus-looking thing in his box of raisin bran? When he spills his cereal milk on it, it turns into a garden gnome.
Eventually it dries back out into the mummified doppelganger. Whatever fluid he pours/spills on it, the doppelganger turns into something different. I dunno. So much possibility...