Well.... my mind is officially blown.
I guess there is a hidden feature of McDonald's French fry boxes for our entire lives?
Someone posted a tweet with the realization that the cardboard flap on the top of the box has an actual functional purpose on McDonald's fry boxes.
Apparently, you're supposed to fold it back and use it as a place to put your ketchup.
No one knows if that compartment was specifically made by McDonald's or if it's just someone's hack?
As of now, McDonald's hasn't weighed in on it.
Either way, definitely something worth trying next time you roll through McDonald's!