People do this all the time, as far as the voice/character chance thing goes.
I had a buddy in HS that would completely change depending on the people he was kicking it with. His music style would change, clothing style, etc. People naturally try to fit in with other crowds and the crazy thing is, sometimes they don't even realize it. It's a really annoying trait though.
Just because you code switch and take on different presentations doesn't mean you're changing who you are, it's just means you're adapting to more effectively communicate with the person you're talking with. You cant just go unloading a bunch of slang on someone who doesn't understand all that shyt. If Obama went out to hang with Puff and started droppin all types of slang and the N-bomb, yall wouldnt be like " Oh that muthaphucka fake ! ". So why are other races expected to only express themselves in only one manner ?? Being able do have different but genuine sides to your personality doesn't mean you're fake , shyt just means you're well rounded, diverse, and cultured. That coonish mentality that you have to just act one way at all times is almost as ignorant as saying education is just for white ppl.