If you can imagine a “Prisoner of Zenda” with musical numbers, then you’re halfway there with this rather mixed up hybrid. We even have another “Rudolph” (Carl Brisson) who has been neglecting his queen (Mary Ellis), so she absconds from their palace telling him she shall only return once he mended his ways. Now the king does actually quite like his wife, and so when his beardless doppelgänger “Rover mais...