VIDEO : Surprise! Justin Bieber Joins Ariana Grande in Concert Again, Gets a Little Flirty

Ariana Grande fans were in for a special treat last night: A surprise performance from Justin Bieber ! The Biebs joined his pal onstage at The Forum in Inglewood, Calif., where he first accompanied her for a performance of "Love Me Harder". Justin and Ariana got a little flirty with their dance moves. And while the Biebs didn't get too grabby, it seems he was still too handsy for Ariana's boyfriend Big Sean. The rapper reportedly tweeted (and quickly deleted),"This kid is about to learn not to touch my girl like that. Beliebe that."??