On Wednesday night Ariana Grande performed at The Forum in Inglewood, California, and Justin Bieber made a surprise appearance for "Love Me Harder," and he also sang his own tunes, "As Long as You Love Me," and "Where Are U Now." Scooter Braun manages both of the stars and Bieber joined Ariana onstage last month in Miami so this isn't a shock, but we WERE stunned to see how handsy the Biebs got with Ariana!

UPDATE:
While it was initially reported that Ariana's main squeeze, Big Sean, was furious over the onstage PDA, his team is denying that there's any drama. There was a screen capture of a tweet that appeared to come from Big Sean's Twitter account that read, "This kid is about to learn not to touch my girl like that. Beliebe that," but his publicist claims the tweet is fake. No word on who put it out there in the first place, but TMZ posted a picture of it, and other websites posted a different tweet from an account that appeared to be Big Sean's. The other tweet was a photo of Bieber all over Ariana with Big Sean seemingly writing, "Wow."

The last time Justin joined Ariana onstage he totally messed up the lyrics to "Love Me Harder," and this time he was able to get through the whole song without any screw ups. Before the show, JB tweeted, "What should I do tonight? Hmmmm" and after he added, "Love the stage. Thanks for having me @ArianaGrande and thanks LA. Gotta tour again soon :)"

Click thru to see complete videos of all three songs!