From a teaser the boys recorded, we got a glimpse of the guest list, which includes Robbie Williams, Celine Dion, Simon Cowell, Kelly Rowland, Piers Morgan, The Muppets, Khloe Kardashian, Nicole Scherzinger and tennis player Novak Djokovic.
But the list isn't limited to those people. That's why MTV News has created our celebrity guest list for the event.
The boys have a bit of a rough history. And although we'll never know if their petty beefs have been put to bed, it would be cool if the two boy bands reconciled on the live stream — for all to see.
And since things should be all about love this weekend, why not bring along a few people that have shown the guys love in the past. Remember when Niall and Katy kissed after they won Best New Artist at the 2012 VMAs? So cute. Plus, we know Niall's looking for a girlfriend.
Speaking of girlfriend material — Demi has had to dodge romance rumors with Niall before, especially after they were seen together after those same VMAs. The live stream is the perfect place to go public. So just come out and admit it already!
We know big sis Khloe is coming, so bring along the fam! Plus, Kendall's been getting awfully friendly with Harry. They were photographed hanging out in Los Angeles on Thursday. Perhaps they were tossing around ideas for 1D Day?
The Backstreet Boys
While One Direction are showing off the new(ish)-fangled technology for their Google Hangout and YouTube sesh, why not give the same opportunity to a boy band who didn't have the chance to do a seven-hour live stream. Was the Internet even invented back then?
We already know that 1D have a fan in Mother Monster. The seashell-wearing singer coached the guys backstage at the 2013 VMAs and gave them a little advice. Surely, she could take time off from her ARTPOP whirlwind to make a cameo.
After Niall said he would want "Harry Potter" actor Tom Felton to play him in a biopic,
Draco Tom agreed, telling us, "I'm a big Directioner." So here's an idea: how about we get him to play Niall during the live stream. You know, like Rupert Grint did in that Ed Sheeran video? Time to crack out that British sense of humor.