"There were over 2,000 kids that day," Casella recalls. "Her mom Lynne had driven her eight hours to the audition and Britney had to wait another eight hours to get in the room."
But once she started singing and dancing, "I knew a star was born," he says.
Spears, now 28 and rebounding from a series of personal and professional setbacks, was the perfect little lady that day.
"She called me 'Sir,'" says Casella. "I told Britney and her parents that I would do whatever I could to help her dreams come true."
Casella takes part in a new ABC show Rediscovered, premiering Dec. 23. Hosted by Donny & Marie, the show seeks out non-famous, one-time aspiring stars, and gives them a chance to live out their fantasies of pop stardom.
Along the way, viewers can see samples from Casella's collection of long-lost audition tapes with the likes of Justin Timberlake, Jessica Simpson and Ryan Gosling.
"This show is about making childhood dreams come true," says executive producer Dave Broome. "What makes this show so different is that, unlike other competition shows, none of our contestants applied. We tracked them down, surprised them, and plucked them from their daily lives for this once in a lifetime chance."