I think I have a possible answer to Eric’s question, also, although we’d have to do some research on the exact chronology. In Cole Porter’s Kiss Me Kate there’s the great song ‘Brush Up Your Shakespeare’, which has great rhymes. One of them, of course, is:
Just declaim a few lines from Othella
And they’ll think you’re a hell of a fella
If your blonde won’t respond when you flatter ‘er
Tell her what Tony told Cleopatterer
Here the motivation for the extra syllable is clear, but Kiss Me Kate premiered in 1948, so the silly pronunciation may have been floating around. But the film was dated 1946, so maybe not. According to imdb.com the soundtrack of Till the clouds roll by was the first ever released of a live (as opposed to animated) movie.
Anyway, tiny additional amount of data from a Broadway freak…