Hi everyone! Thank you all for the help.

I found another way to copy the model with blendshapes and to make the model have the same animations as the original model (without adding bones and joints, and no skinning for the duplicates.) In order for this to work, your original model should be skinned, and have blendshapes.

It goes like this:
1. click you original model
2. Click Edit>Duplicate Special>Duplicate Special options box.
3. In the dialog box choose instance for the Geometry type, the smart transform box should be checked, and everything else should be left with the default settings (edit>reset settings).
4. Click Duplicate Special, and move your duplicate somewhere.