I seldom eat at McDonald's, but it I'd love eat an Egg McMuffin just to see this!
The giant egg billboard starts cracking and opening up in the wee hours of morning. By breakfast time, the egg has already hatched, and you can see "Fresh Eggs Daily" written on the egg's yolk.
The egg stays open from 6:00AM till 10:30AM, to indicate the availability of fresh eggs during that time. Once the breakfast time is finished, the egg billboard shuts and stays closed as a whole egg till the next morning.
Thanks to Jo for the pictures.