Someone on that show seems to have had a real eye for talent and star potential even in singers/actors that were still children. I don't know it was the casting director, a subordinate, a producer, or someone else. They cast Keri Russell in 1991 and Justin Timberlake, Britney Spears, Christina Aguilera, and Ryan Gosling in 1993.
According to IMDB it was Matt Casella
As Casting Director for The Walt Disney Company and Jeffrey Katzenberg, Matt Casella auditioned over 85,000 kids during 1988-1994 for "The All New Mickey Mouse Club". From these auditions, which he did by holding open calls throughout the United States and Canada, Matt discovered, directed and launched the careers of: Justin Timberlake, Ryan Gosling, Britney Spears, Christina Aguilera, Keri Russell, JC Chasez and Tony Lucca, among others.
In an interview Casella said.
"I knew how special these kids were when I saw them," says Casella, who saw 20,000 kids during four years of auditions. "There was sort of an eagerness and a sparkle in their eye that said, 'I want it.
Tony Lucca (an ex-Mouse Clubber) said
“...But Matt Casella, the casting director, has an impeccable eye for talent. He really bats 1.000. There were a couple of times maybe, where he was off [laughs] but he cast some pretty big projects over the years, but the Mouse Club was definitely his crowning achievement in that he identified something in all of us that he just see in other people. He realized that there was an inherent passion and desire and ability in all of us.