it is a true medical syndrome, i english geordie woman woke from an accident and spoke in a rasta accent, the post above and also recently a school boy who woke with a posh royal type accent.
there is actually a medical term for this. theory is that the brain has taken in words from tv,internet etc... and does know how to translate somehow. apparently most go back to speaking there natural tongue but apparently it does happen.
ive never come across it and had not heard of this till recently when it was in the press, im dubious about it but there nothing i see saying its fake anywhere and the fact theres more than one case.