The reason that Dan Dailey sings "Friendly Island" in such an odd voice is that he is making fun of Ezio Pinza the basso profundo opera star who was starring in the then current stage show "South Pacific".
This movie does a parody of the musical South Pacific (1958), and Mitzi Gaynor would go on to star in the movie version.
Feature film debut of Mitzi Gaynor - who had only been in a previous film short billed as 'Mitzi Gerber.'
Mitzi Gaynor also starred with Dan Dailey in There's No Business Like Show Business (1954). In that film she played his daughter.