Yesterday I found an amusing short film called Fluent Dysphasia, which tells the story of an Irish man who wakes up one morning after a night of heavy drinking to find that he speaks Irish fluently and can no longer speak or understand English. Beforehand he spoke nothing but English, so he is very surprised and worried by the change. His best friend thinks he’s gone mad or is possessed, and the only person who understands him is his daughter.
Recently there was a real life case similar to the one portrayed in the film – a Czech motorcyclist who started speaking English fluently after an accident. In this case, his English fluency disappeared again after a few days and he had no memory of it.