Jonathan Harris, of "Dr. Smith" fame was an American actor (born, I believe in Brooklyn) and worked very hard to lose the "Nooyahk" accent he grew up with. Apparently later in his career he was asked about his "British" upbringing, when he responded "I'm not British, just affected."
I originally posted the above in someone else's "desperate plea for help" thread, but it probably belongs here.
I worked with someone awhile back who would every so often drop into a faux affected German accent when reporting technical data. I guess she thought it made her sound smart, but it only confirmed her status as a whack-job.