Download the app and point your phone's camera at a friend, and it will convincingly map their face, in real time, onto someone else's: yours, a baby's, Beyonce's.
Since appearing in the app store about a month ago, the app hasn't strayed far outside of Apple's most-downloaded offerings.
And while the technology isn't perfect - the app's first truly ubiquitous meme was a disastrous face-swap between a dad and his baby - the results are lifelike enough of the time, that the Daily Dot called it "creepy".
"It's a lot of fun," said Jason Laan, one of the app's two creators. "But behind the fun, there's some really amazing, hardcore technology."
Laan, a chemical engineer by training, has a long history of turning serious tech to more frivolous purposes: In the eight years since he founded his app development firm, Laan Labs, he estimates that they've launched around 50 products, from Tap DJ to Dog Vision HD.
But for Laan, computer vision - the science of training computers to extract and understand information from pictures, the same way humans do - has always possessed a special intrigue.
Researchers at places like Google and IBM, with their extraordinary 3-D cameras and lightning-fast processing speeds, had enabled computers to catalog objects, recognise faces and even interpret feelings.
Laan and his partner, Will Perkins, began wondering if the iPhone's improving camera and processing capabilities would allow them to try out similar projects, albeit less seriously.
So late last winter, Face Swap Live was conceived. The app that has since launched a thousand YouTube
But the appeal of the face-swap has always been its weirdness - the degree to which it inverts and diverges from reality. The best face-swaps are also the most surreal: Tom Cruise as Jack Nicholson, Barack Obama as George Bush, Nicholas Cage as literally everybody.
"There's something about absurdity that gives Internet memes a lot of traction," said Britney Summit-Gil, a doctoral student at Rensselaer Polytechnic Institute who studies Reddit culture.
"Absurdity has a long, storied history of entertaining humans." And it's not so different from awe, she says - one of our more viral emotions.
Oddly enough, however, we're moving closer to a world where face swaps are both less "awesome," in the sense of inspiring wonder, and less obviously absurd.
Thanks to innovations like the ones that spurred Face Swap Live, face-swapping no longer requires any time at all, to say nothing of expensive editing software and human effort.
With better cameras, Laan and Perkins say (3-D cameras, particularly, like the ones Intel just unveiled at CES), our smartphones could do far more than copy-paste a face.
Already, Disney is working on a technology that can map your face down to its individual wrinkles.
At Stanford University and Germany's Max Planck Institute, researchers have developed a technique that photo realistically transfers one person's facial expressions to another - not face-swapping, in the traditional sense, but face-hijacking via algorithm.
These researchers believe we're moving closer to a world where remote workers can Skype into meetings half-clothed, their faces mapped onto a body in a business suit. They suspect we'll be able to tweak actors' bad takes and zap unsuspecting bystanders from live TV news.