"Carey and Nicki went at it during the first "Idol" taping on Sunday in NYC. When Nicki started critiquing a contestant, Mariah would interrupt -- not once, but many times. Each time Mariah interrupted, Nicki fought back by loudly talking over Mariah. 

According to an insider, Mariah and Nicki tried to cover their disdain for each other but everyone saw through it, adding, "These girls just don't like each other."