Deleting the insides of model/ hollowing it Hi i'd like to ask if i can delete all the faces and vertices from in side my model, 

Here's my model, it looks fine, but there's problems, like some parts of it have two faces so it sort of glitches. (near the back of the foot)



And also, i used ALT + E to extrude individual faces, that made all of inside of it just horrible, and i want that the whole model to be hollow in the inside, like so

This is a cube


And this, is inside of my model,



So, my question is, can i delete all this messy blocks inside of it without any noticeable changes on the outside? 

Also, i'm sort of new to blender so please tell me what you mean and how i would do it. Thank you.
You can use the Select Inner Faces operator,  and then delete then. To do this, in 3D view space, go to the header, then Select, then Interior Faces. Then you can press X > Vertices.