What was Jamaican sprinter Usain Bolt smiling about as he coasted to victory in the 100-meter semi-finals? Social media users have many theories, and one involves Richard Simmons.
It's the image that may ultimately come to symbolize the brilliant career of Jamaican sprinter and world record holder Usain Bolt.
But for now, the internet's going to take the photo finish and run with it.
One Twitter user wondered if the photo somehow caught Bolt during a moment of personal self-discovery.
Another thought Bolt's quick glimpse back might have cost him a potential world-record-breaking run.
Yet another fan saw in the photo a moment just made for a documentary voice-over.
Yet another was reminded of the Road Runner cartoon character, forever outwitting the coyote in classic cartoon style.
Then things started getting weirder and more Photoshoppy, because, you know, the internet.
One theory was that Bolt had been momentarily rattled by the appearance of American fitness guru Richard Simmons.
Another appears to have seen a parallel between Bolt's performance and current US election polls.
One Twitter user, meanwhile, wondered if only a fictional character could defeat the Jamaican sprinter - namely, Dash from Pixar's "The Incredibles."
Many, many others, however, took to Twitter to simply praise Bolt's outstanding performance after he won his third consecutive Olympic 100-meter dash (a record) in what the Jamaican sprinter says was his final Olympic event.
In a night of superlatives, it was Usain Bolt himself who ended up providing one of the evening's best reactions.
Here he is learning about the world record 400-meter run by South Africa's Wayde van Niekerk.
Since many social media users tend to (illegally) download, upload and modify copyrighted photography, it's worth giving credit where it's due here: The instantly iconic image of Usain Bolt's smiling look back was snapped by Australian photographer Cameron Spencer during the men's 100-meter semi-final race.
Expect to see it for a long time to come.