I don't know the woman who sang "Poor Unfortunate Souls", but she's on the far right in the picture, & she was terrific. (Found her - Kerry O'Malley.) I learned tonight that they'd originally wanted Bea Arthur to voice Ursula, but that didn't work out. Charlotte Rae was also in the running, but that didn't work out either.
"Proud of Your Boy" (which was cut out of the animated film "Aladdin" but included in the stage musical) was sung by the man on the left of the picture, who I don't know. /3