Waking up speaking a foreign language perfectly, or at least upgrading an accent

In the yeah, maybe category: There's the Czech teenager who had just begun studying English and woke up in an ambulance post-auto accident not knowing he was Czech and speaking perfect English with a clear English accent. It did not last.
Then, there's this 10-year-old from York who got a more upper class accent after neurosurgery for meningitis. He couldn't understand why he was being stared at when he first spoke in this manner. Initially, he had lost his ability to read, write and recognize different objects. Eventually, he recovered.