It's official. When I speak to them, all my sons must hear are those funny, muted trombone sounds that the Peanuts' characters heard when adults spoke in their world. Today I looked directly at C and made a request. He deigned to notice that I was actually talking to him, turned his face toward mine, and parroted back to me perfectly, "Mwa-mwa-mwa-mwa-mwaaa." Those 'words' exactly.
So that's why I can never get them to put their shoes and coats on in the morning when it's time to leave the house. The mystery has been solved.