Doctors say Mrs Roberts, who was born and bred in Indiana, has a condition called foreign accent syndrome. | This rare condition occurs when part of the brain becomes damaged. This can follow a stroke or head injury. There have only been a few documented cases.
–Stroke Gives Woman British Accent (BBC)
This article conflates the meaning of “accent” with “dialect,” but so do plenty of other people, so I’m being terribly pedandic by pointing it out. In other news, muppets everywhere are turning Swedish. (That’s a joke from an old “The Muppet Show” skit, which I sadly can’t find any significant reference to online. I believe it was in 1979 and the guest star was Jonathan Winters. Bork bork bork!)