But on Monday, Mariah buttonholed Nicki and the 2 agreed ... a feud wouldn't be good for the show, so they buried the hatchet and walked down the hall smiling, hand-in-hand.
Mariah Carey pulled Nicki Minaj aside yesterday and convinced her ... feuding would not be good for the show, and they both needed to stop the antics they pulled during Sunday's auditions.
"American Idol" sources tell TMZ ... Mariah and others were ticked off Sunday that Nicki arrived 45 minutes late ... and that set the tone for the whole day. Although Nigel Lythgoe is saying everything was hunky dory Sunday, we know it wasn't. Mariah talked over Nicki, criticizing her critiques, and Nicki fired right back.
But here's the thing. We're thinking a feud is exactly what "A.I." needs.