So I have a few comments on this. First off, you were at Disney World and you didn't stop by to say hello? I'm shocked!
Second, the first thing that threw me was what initially appeared to be a shadow cast by the object. My first theory was something wsa thrown or ejected right at the moment that the image was taken. But that would not explain the shadow.
Then when I enlarged the photo I saw it was not a shadow, but rather the object had some real depth to it. Depth being relative since I believe it to be somewhat close to the lens.
So, after seeing this I would have to say that I believe this object to be a camera strap or something very similar that got into the frame at the instant that the flash fired. Hence again the danger of using a camera top flash. There are a ton of effects created by this. If you must use a flash the preferred method is by using a external side facing flash.