Michael Phelps reveals what was really going on in that furious 'game face' photo

Michael Phelps is known for his big ol' grin as as much as his swimming prowess

However you might remember a different face he made on Monday during his 200m semifinal preparation.

Behold: The Stinkface

The death glare of doom appeared to have been directed towards rival swimmer Chad le Clos, who had beat him back in 2012 and was preparing for the swim by shadowboxing around Phelps.

The image swept across social media as people tried to make sense of what was going on.

One man even got the face tattooed on his leg...

Was he calling forth The Demons? Preparing to pounce on le Clos?

Turns out the real reason he pulled the infamous face is much less exciting, as he told Today on Tuesday:

I just had music going on in my head. I had thoughts going on in my head, spitting water a little bit all over the place, so I was in my own zone. I was not intentionally mean mugging him or giving him a dirty look.

See? Totally innocent.

More: Man's Olympic dreams ended by his own penis

More: Rio 2016: Photographer behind Usain Bolt image explains how he took it