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Justin Timberlake And Selena Gomez Surprise Taylor Swift's 1989 Tour: Watch

Phoebe Buffay also comes out for a 'Smelly Cat' duet.

LOS ANGELES -- Taylor Swift is looking up. Her eyes, glimmering, circle the Wednesday night crowd at the Staples Center, which is lit up with custom-made 1989 World Tour bracelets and homemade signs of glitter and puff paint. You see her winking at the fans in the 312 section before she lifts her gaze to the newly adjusted banner on the wall. Next to the L.A. Lakers' championship flags floats her name in big block letters. "Taylor Swift: Most Sold-Out Performances," it reads.

She has, yet again, broken another record.

"You, with your words like knives and swords and weapons that you use against me," she sings, swinging her guitar in front of her for an acoustic performance of "Mean," a song she wrote about an unfriendly critic years ago. She's towering above thousands of fans -- teens with cat ears, grown men with T.S. shirts, couples waiting for their song -- and you can't help but think that the 2010 song is even more meaningful in 2015, after her 1989 album went five-times platinum, her "Blank Space" video has been viewed over a billion times and she's up for nine Moonmen at the 2015 MTV Video Music Awards on Sunday.

"And I can see you years from now in a bar… Drunk and grumbling on about how I can't sing."

She pauses.

And pauses.

And pauses.

And for every beat she stays silent, the screams get louder. She shrugs. She soaks it in. She lets you imagine what her life would've been like if that mean critic had actually gotten inside her head, instead of fueled her to become greater. And then, just as the screams reach peak decibel level, she sings the anticipated next line. "But all you are is mean."

It's the last night of her five-performance run at the Staples Center, and not only is she surrounded by hoards of Swifties, but her celeb friends are watching from the sound boards -- Ruby Rose, Miranda Cosgrove, Emma Stone, among many more -- even boyfriend Calvin Harris is there.

Of course, it wouldn't be a Swift concert if there weren't a few surprises, and she tells us that if we're generous with our audible admiration, she'll bring some special guests out.

Taylor introduces Selena Gomez as one of her best friends, a talented, beautiful, intelligent woman with the song of the summer (Taylor publicly voted for Sel's "Good For You" for the Song of Summer VMA on Twitter last week). They strut down the catwalk, beaming at each other while they sing "Good For You" -- perhaps remembering their 2011 duet at Madison Square Garden.

Taylor promises that that's only the first surprise of the night, and shortly after, she's introducing a lesser known artist, who's only ever played in coffee shops before, "so be nice to her."

"Phoebe Buffay, everyone!" she yells, nearly squealing, to the crowd's delayed reaction. Lisa Kudrow walks onstage with an acoustic guitar as her character from "Friends," one of Swift's favorite '90s sitcoms (Kudrow's appearance comes just three nights after she brought "Friends" actor Matt LeBlanc to the tour).

Online, you'll hear jokes about the different people Taylor invites to the 1989 Tour -- whether she'll run out of guests, how she manages to wrangle such high-profile celebrities, if it's just for show -- but you'll never see Swift happier than the moment she sang "Smelly Cat" with Kudrow.

She plays her 1989 hits, of course -- "Bad Blood," "Style," "Are We Out Of The Woods" -- and she throws it back to old songs like "Mean," "Love Story," and "I Knew You Were Trouble." She even mashes up the old and new, sewing together "Enchanted" and "Wildest Dreams" into a silky, inspiring ballad at the piano. But there's another song she wants to sing -- and it requires the help of one of her all-time musical crushes.

Nobody can hold it together when Justin Timberlake pops out from beneath the stage to sing "Mirrors," his first performance since becoming a dad in April.

It's hard for JT to leave the stage after the duet. He keeps running back down the catwalk and lingering next to the guitarist. Clearly, he just wants to stay and have fun with Taylor too.

But after two and a half hours, she leaves us with a "Shake It Off" dance party and about a dozen bows. As nearly 20,000 fans rifle out of the Staples Center, shuffling their sore feet through piles of confetti, each person touched by Taylor, you realize her impact. She brought all of us here for the love of music; she invited all her friends to perform for us; she inspired us to never give up on our dreams -- despite the haters (who are just going to hate, hate, hate). She told us to forget the meanies.

And, yet, she only wants one thing from us: "If you could possibly be kind to yourself, as much as you possible can, that would make me so happy."