Several people have sent me links to this recently-posted video:
I've noticed that people who are good at imitating accents and languages often associate each imitation with a different setting of postures, gestures, facial expressions, body-movement patterns, etc., as this woman does.
Some other posts on doubletalk-ish things:
"Yoghurt medley", 7/23/2010
"What English sounds like if you have Wernicke's apahasia", 10/22/2011
"How Sid Caesar learned double-talk", 2/13/2014