I grew up around fairly heavy southern US/Appalachian accents. I lost most of mine, partly through (I think) several years of speech therapy when I was little. I then lived in bigger (but still Southern) cities for six years, followed by Philadelphia for 18.
The guy I'm tutoring through the literacy council has a very thick South Philly accent.
At certain times, hilarity ensues from the combinations of accents.
[Word in a book: Past]
Him: Pass'
Me: It's Past.
Him: Oh, Pass'
Me: Pas
T
Him: Pass'.
etc.