The Weeknd and Selena Gomez didn't let a little thing like ZERO Grammy Awards stop 'em from hitting the post Grammy party scene.

The couple hooked up to hit Rihanna's party at 1 OAK on the Sunset Strip. He performed during the award show, one of the night's highlights, but it appears his gf was a no-show. Selena wasn't nominated, and neither was The Weeknd -- "Starboy" was released after the cutoff date.

His hit record did get a shout-out Sunday night, with a heaping side of SHADE, from Justin Bieber.

As we told you ... Justin bailed on the Grammys this year, but during the ceremony he went live on Instagram and took a shot at his ex-gf and her new man.

Ice cold.

You'd think Ed Sheeran -- a 2 time Grammy winner with 9 more nominations -- would breeze into a Grammys after-party but NOOOOO!

Ed hit up Milk Studios in L.A. for the shindig but the front door proved elusive, and not just for him. Adrien Brody and super DJ Pete Tong also got the cold shoulder.

NeNe Leakes had trouble making her entrance but managed to make it in later in the evening.

And worst of all ... they ran out of In-N-Out burgers.

Watching Beyonce and Adele go head-to-head at the Grammys is like watching Roger Federer play Novak Djokovic, Muhammad Ali vs. Joe Frazier ... at least that's the way The Game sees it.

The Game skipped the Grammys -- he wasn't nominated -- but he did weigh in on Adele beating Queen Bey for the night's top 3 honors Sunday on his way into Playhouse in Hollywood.

Game also makes it clear ... Grammys ain't his thing.

The Grammys were pretty slick if you watched on TV, but lots of other stuff happened at Staples Center that was a little less produced.

Lots of big stars hobnobbed it when the cameras weren't trained on them.

John Legend was hit by a flash mob at GQ's Grammys after-party at Chateau Marmont, but the big star was Grammy winner Chance the Rapper.

Skrillex, Bella Thorne, Teyana Taylor, Taboo and lots of others partied super late.

Beyonce just hit the stage -- plus 2 -- at The Grammys and kept things low-key ... sitting for most of her performance.

Bey opened her set with a video montage before appearing on stage at Staples Center to sing "Love Drought" and then took a seat for "Sand Castles." She also recited poetry from her Lemonade album. 

The singer kept movements minimal ... taking a seat for most of the performance. 

It's the first time we've seen Beyonce since the announcing she was pregnant with twins.

To nobody's surprise, everyone was on their feet when she wrapped. 

The Grammys brought out huge and diverse stars from pretty much every genre of music ... and most of them glittered.

Check out the range.

Josh Dun either didn't think Twenty One Pilots would win a Grammy, or he's just messing with us ... but he insists he didn't give a thought to his underwear when he got dressed for the show.

We got Josh at Milk Studios for a big after-party, and he doesn't understand why people are making a big deal about a bunch of guys watching the Grammys together in their skivvies. 

John Travolta did a funny callback to his "Adele Dazeem" 2014 Oscar blunder ... problem is, a lot of people didn't remember.

Travolta was leaving the Interscope after-party in WeHo Sunday night, when he had to do what funny people dread ... explain his joke. John pretended he couldn't read the teleprompter when he introduced Carrie Underwood and Keith Urban.

You may recall -- or not -- John introduced Idina Menzel at the 2014 Oscars as "Adele Dazeem." 

Madonna had multiple good reasons to end her custody war over Rocco ... if she didn't, her bid to adopt two kids from Malawi would have come to a grinding halt.

The judge who green lit Madonna's adoption last week spent a long time understanding the circumstances surrounding her custody dispute with ex-hubby Guy Ritchie ... so says an official from the Malawi courts. We're told the dispute was of "paramount concern" because the judge didn't want the adopted kids thrown into a "toxic" family environment.

Since the case settled and all seemed copacetic with Guy, the judge gave the thumbs-up.

As we reported, Rocco bailed on Madonna a year ago during her tour and moved to London to be with Guy. Rocco now spends the school year in London and summers in NYC.

A court-appointed guardian will travel to the U.S. and evaluate the family dynamic before the adoption's finalized.