Opening night of Jennifer Lopez's "All I Have" Las Vegas show was packed with A-list celebs who got up on their feet to worship the booty ... and dance. 

Seriously, it could've been a Hollywood award show -- Justin Bieber, Scooter Braun, Ryan Seacrest, Rebel Wilson, T.I., Rosie Huntington-Whiteley, Kelly Osbourne, Hoda Kotb, Derek Hough, Nicole Scherzinger and many, many more.

Her "Shades of Blue" co-star Ray Liotta was also there ... and BFF Leah Remini took in her second performance. And onstage, she had Ja Rule, Ne-Yo and Pitbull performing. 

She gave 'em what they came for too -- singing, dancing, and yeah ... lots of booty shaking.

6:51 AM

Rapper Mike Stud is no dummy ... putting his smokin' hot model GF Josie Canseco front and center (in a thong) in his new music video for his song "Anyone Else" ... and TMZ Sports has the footage. 

Stud and Josie -- daughter of the baseball legend -- have been dating for a while ... and Stud wrote the song about her.  

You gotta watch the entire thing ... Josie (who's already been featured on SI.com) flaunts her insane physique while eating pizza and a grilled cheese sandwich. 

6:30 AM

Slow down, Jelena fans -- yes, Justin Bieber and Selena Gomez hung out Wednesday night ... but they are not dating again. Not yet anyway.

The reunion of everyone's favorite on-again/off-again set the Internet on fire, but here's what really went down.

Pastor Rich Wilkerson Jr. -- who counts Bieber and the Kardashians among his flock -- posted a series of videos from a gathering Wednesday night in L.A. ... and both Bieber and Gomez were there.

According to our sources, the exes were cordial, but that's it. In fact, Bieber brought rumored girlfriend Hailey Baldwin with him -- another sign there's no reunion on the horizon.

We're told this isn't the first time Bieber and Gomez have been together lately -- they've both been to a few of Pastor Rich's gatherings in recent weeks.

So, no romantic sparks for now. Give it time, they'll be back together -- and broken up again -- eventually.

5:06 AM

Justin Bieber may be juggling sisters, because he partied Tuesday night with Kendall Jenner at the same night club where he hooked up with Kourtney Kardashian over the weekend.

Justin and Kendall arrived separately at The Nice Guy in WeHo at around the same time -- 10 PM.

They left separately, too ... just like Friday night when Justin and Kourtney left Justin's go-to club and headed for his Bev Hills hotel, where she stayed 'till 4 AM.

8:46 AM

Tyga and Kylie Jenner are together even though they act like they're apart -- not exactly the way the real world works ... but their world's a whole other thing. 

As we've been reporting, our Kardashian sources say they've made a deal which was mostly Kylie's doing ... that they each give each other space professionally, so it doesn't mess up their respective brands.

That's why they showed up separately at the 2nd Annual Diamond Ball Thursday night at the Santa Monica Airport. 

Rihanna threw the ball and it sounds like Kylie's taking a page from RiRi's playbook.

5:23 AM

Justin Bieber may be juggling sisters, because he partied Tuesday night with Kendall Jenner at the same night club where he hooked up with Kourtney Kardashian over the weekend.

Justin and Kendall arrived separately at The Nice Guy in WeHo at around the same time -- 10 PM.

They left separately, too ... just like Friday night when Justin and Kourtney left Justin's go-to club and headed for his Bev Hills hotel, where she stayed 'till 4 AM.

3:32 AM

Daphne Joy -- best know for this, and being 50 Cent's baby mama -- is a sight to behold from almost every angle you can imagine ... but especially from behind.

Daphne's got a 3-year-old kid with 50 Cent and is rumored to be dating Jason Derulo now. She pretty much gave away the secret to her dating success on the beach in Miami.

Fiddy must love watching her leave.

7:08 AM