Could I create a seperate unit to plug into my laptop that would act like...

...i was upgrading it? I have a hp pavilion which I use for both gaming and college but I would like to add a better graphics card and more ram etc. However I know that this would be almost imposible because of the lack of space so was wondering if I could put them in a tower pc case and somehow connect it to my laptop but still be able to unplug it easily for when I need to take my laptop somewhere else. Does anyone know if this is possible?