Yeah this was some weird mid-30s revelation for me. I KNEW I had heard that song somewhere before, and Robin Hood was always my favorite Disney movie from the ages of like 5-10. Well that and Puss and Boots and inexplicably anything with Donald Pleasance.
I got to see this in a movie theater when I was about five. That rooster terrified me.
All the other characters in the movie were done in a really cartoonish fashion. The rooster alone was done in a frighteningly realistic manner. He had creepy yellow eyes and a big floppy comb & wattles. He even had spurs on his very realistic chicken feet. I can remember another chicken in the movie, but it was cartoonish and fit in well with the rest of the characters.
And to hear a human voice coming out of that monstrosity was very jarring.