Distorted Mesh when fully animated

I need answers to this.

For some peculiar reason, my mesh that my friend animated in Blender seems to be a little… out of place. When I try to play the animation, it seems like it is fluent, but the mesh is distorted. Random parts of the model are everywhere. I am not a big Blender guy, so I really don’t understand this. My friend told me to go on this site to figure out what the problem is. Here is an image so you can see what I am dealing with: