Celebrity Guests Ruled The First Night Of iHeartRadio Festival In Las Vegas

The bill was already packed—then some surprises showed up.

Las Vegas is the ultimate place to throw a party so maybe that's why the first night of iHeartRadio's annual festival was so jam-packed with guest appearances and star collabs last night.

For this year's festival debut on Friday (September 19), Taylor Swift, Nicki Minaj, Coldplay, Usher and more were all slated to appear. But with this many celebrities in one place, others seem to apparate through sheer force of will. Here's a run-down of the highlights.

Taylor Swift Shook Everyone Off

No new music from our resident wallflower-turned-prom-queen but this spirited performance of "Shake It Off" felt just as much like a kiss-off to her haters than ever, and it did not disappoint.

Chris Martin Takes A Selfie On A Fan's Phone

More like PHONE full of stars amirite?? During "Sky Full Of Stars" Martin just casually reached down, grabbed a fan's phone and took a selfie before returning it.

Why was he in such a giving mood, could it be linked to the J-Law sighting backstage?

Isaac Brekken/Getty Images

Hey girl heyyyy.

Ariana Grande And Nicki Minaj Are Better Together

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Sure, we're still obsessed with "Anaconda," and Ariana always amazes us when she's performing solo, but the two of them together for "Bang Bang"? Now that's priceless. Some things are just better together.

Usher Brings Out Chris Brown

In another surprise move, Usher brought out Chris Brown to perform Brown's latest X single "New Flame." "I'd like to introduce this young man that I've gotten to know," Usher said. "He's a friend, he's a brother, he's a passionate artist and I have a fortunate opportunity to have shared a song with him."

The lineup for tonight is just as packed: Lorde, One Direction, Iggy Azalea, 50 Cent, Ed Sheeran and more—and I'm guessing more surprise guests will be in store. You can watch the whole thing live via Yahoo tonight at 10 p.m. EST.