There is a spectacularly interesting condition that people have been known to acquire upon some sort of trauma to the brain, whereupon the patient wakes up with a foreign accent, even from a place he may have never visited. It's called Foreign Accent Syndrome, and it can come on either externally as in a car accident or internally, as in a stroke. So a woman from Oregon awakens from dental surgery with a Australian accent. Spectacular!
Upon further investigation, however, FAS is actually pretty boring. Well, comparatively speaking. It turns out that, while rare, it's the result of damage to some part of the brain that controls the extremely elaborate process of speaking. With even just slight changes to these areas, the muscles that control the tongue, lips, jaws, cheeks -- all of the parts of the mouth and face that are involved in speech -- may not work in the same way they did prior to the damage. Vowel pronunciation may be especially affected and it's here that the big change is detected by people listening to the person with FAS, giving the patient the putative foreign accent.
If you listen to the woman from Oregon in the link above, you will notice that her accent changes from time to time. Mostly, to me at least, she sounds Australian. But she is described by the site the video is on as having a Transylvanian accent, which you can kind of detect here or there. And at times, you can detect a Welsh or Irish brogue; I can at least.
This is the heart of FAS: the patient's vowel production is affected in such a way that, to people listening, it sounds like a foreign accent. And everyone else, the listeners, generally detect accents they're familiar with, settle on the one that seems most prominent to them and ignore the vowels and other speech patterns that sound more like the accents of other dialects. At least one study has concluded that FAS is largely a condition that is observer-specific. Different people will detect a different accent for the same patient. Which is why the woman from Oregon is described as having a "Transylvanian twang" in the caption under the video. That's what she sounded like to whomever wrote it.
I guess it is fairly neat, actually.