Coachella 2014: Who might surprise?

If the Coachella Valley Music and Arts Festival guarantees festival-goers anything, aside from wickedly high temperatures, it’s this: Leave your expectations outside the gates.

As the festival kicks off Friday, much of the buzz undoubtedly will be dominated by OutKast’s highly anticipated reunion. What will their set look like? How will the pair sound after seven years apart? Do they still have it? And even more, who might possibly join them onstage?

The surprise guest appearance is a festival staple, and Coachella acts have turned it into an art form.

It certainly wasn’t a shock when Rihanna popped up unannounced during Calvin Harris’ set in 2012 to perform the two smashes he produced (“We Found Love” and “Where Have You Been”) and it wasn’t much of a surprise when Jay Z celebrated his 2010 slot as the first-ever rap headliner by calling on his wife Beyonce to join him onstage.

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But no one could have predicted Phoenix’s left-of-center collaboration with R. Kelly last year. Except maybe the ghost of Tupac, whose uncomfortably real likeness at Coachella 2012 has to be etched in history as the most jaw-dropping guest appearance on any stage, ever.

So who will pull out a surprise this year?

As the sun rose over the dusty Indio desert and thousands of music lovers prepared to file into the festival grounds, we combed over the weekend’s schedule for potential jaw-droppers.

Here are six acts we are keeping an especially close eye on this weekend:

OutKast: Seven years is a long time to be on hiatus, especially when you’re one of hip-hop’s most revered groups. Seeing Andre 3000 and Big Boi together at last is enough to satisfy any rap fan. But the duo launching their 20^th anniversary festival run at Coachella is as good an excuse as any to pull out all the stops. Collaborators like Sleepy Brown and Goodie Mob dot a fair deal of the ‘Kast discography, but calling on Frank Ocean for a run through of the “Pink Matter” remix would easily win the Internet.

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Pharrell Williams: Pharrell undoubtedly owned 2013, but the singer-producer had help. Whether with a randy blue-eyed soul-pop crooner, a pair of French robots or an army of little yellow minions, he dominated radio last year – and still is. Those still licking their wounds from Daft Punk’s great psych-out of 2013 are likely itching to see if the duo packed up their vocoder to come deliver the sure-to-be-performed smash “Get Lucky.” And surely there’s someone in the desert who’s hoping for Robin Thicke to drop in for a rendition of “Blurred Lines”?

Guy Gerber: The Israeli techno DJ might fall under the radar among a meaty slate of marquee EDM acts like Skrillex, Zedd and Calvin Harris, but there’s one burning question about Gerber’s set – will he preview that long-gestating P. Diddy-collab album. And will Puffy be on hand to convince us that his foray into dance shouldn’t be written off?

Jhene Aiko: Her sultry, emotive hooks on songs from the likes of J. Cole, Wale, Big Sean and Drake made her hip-hop’s new “it girl.” Any of those MCs could pop up for a scene steal. At the top of our wish list? Drake. He helped boost Aiko’s breakout by taking her out on the road last year and calling on her to support him during his “Saturday Night Live” gig. Her bone-chilling hook on his track “From Time” will play nicely, regardless of his presence, but we can dream.

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Disclosure: Yes Disclosure was on last year’s bill and their perfectly crafted dance floor filler “Latch” provided the perfect close to the festival. But the British duo are bigger stars now, with a bigger stage on which to unpack their deep house tunes and, hopefully, some of the vocalists who helped them out. AlunaGeorge -- a no-brainer, considering they will play a few hours before Disclosure takes the stage. What we’re really hoping for is a surprise appearance from Mary J. Blige, who delivered an excellent remix to album highlight “F for You.” To add fuel to our own speculation, Blige’s Twitter profile currently features a photo of her face covered with the duo’s trademark white outline.

Nas: The prolific rapper is celebrating the 20^th anniversary of his seminal debut, “Illmatic,” by performing the game-changing album in its entirety on a spring tour that will be launched at Coachella. Nas recently trotted out Q-Tip, one of the album’s collaborators, during a performance on “The Tonight Show With Jimmy Fallon.” Was that a preview of things to come? He’s certainly gotta have something up his sleeve for the Coachella crowd.