The Cinderellas were three girls from Hoboken, New Jersey, Julia Veronica Petronzio, Joyce Eyerman, and Josephine De Pasquale. They started out as the Three J's (Julia, Joyce, and Jo) after winning a talent contest on the Ted Mack Amateur Hour television show (a 1950's version of American Idol). This earned them a performance at Madison Square Garden where a talent scout heard them and introduced them to his boss, Buddy Kaye. They made three records in 1959 on Columbia and Decca, plus one where they were backing lead singer Henry 'Gaddy' Wilson. The girls were very young, ranging in age from 11 to 13 years old, when they started making records together!
Billboard Magazine - 9 February 1959
Here's Mister Dee-Jay by The Cinderellas on Decca 30830 from 1959:
We're not taking requests and dedications on MusicMaster Oldies either. Well, at least not yet. That doesn't mean I wouldn't love to do that someday!