Unfortunately, The Biebs forgot some of the lyrics, but apologized to Ari and the crowd.
Next up, they sang Bieber's As Long As You Love Me, which originally featured Miz Grande's boyfriend Big Sean on it! But since Big Sean wasn't on the stage, the pint sized singer rapped his part instead (below)! They finished off with All That Matters.
And sadly for Frankie Grande, he couldn't be there to see the special moment because he was at the Kids' Choice Awards, but don't worry, he made a reaction video.