Even the biggest pop stars can have a brain fart!
As he sang the parts originally performed by The Weeknd, Bieber accidently messed up a few of the lyrics because he didn't remember them completely.
"So I feel bad, I forgot the words Ariana," he told Grande while performing inside the American Airlines arena. "I've been trying to memorize them backstage for like an hour!"
But don't worry music lovers. Grande wasn't upset at all about the mistake. In fact, the duo continued to perform two songs including Bieber's hit "All That Matters" and "As Long As You Love Me" with Grande taking over the rap verse originally performed by her boyfriend Big Sean. Yes, it's a small music world.
As for Frankie Grande's reaction to the special collaboration, let's just say he had tears of joys…literally. In a new YouTube video, the Big Brother alum broke down in tears when listening to the duet live.
"Love you Justin. I love you Ariana," he said while traveling to the Kids' Choice Awards. "Why can't I be in two places at once?!"