I hit some key combination by accident and created this weird box that looks like a bounding box, but isn't, and I can't figure out how to get rid of it.

A screenshot is here: http://farm8.staticflickr.com/7382/10659944165_6ec30aa9ce_o.jpg

It seems to be actually part of my mesh, because if I start a new blender project and append this object into it, the weird box comes with it. I can't find any child objects in the scene tree. If I try to select just the hat in edit mode and separate it, I'll get the box too. If I move the hat outside of the box and try to separate it, I'll get a copy of the box, but not of the hat. I'm worried this is going to mess things up for me when it comes time to align the hat with a character.