This Easter Egg is still in the cooker. It’s a flavor message that will pop up when you click on an egg you are incubating. The purpose and the reason is unknown at the moment. Here is the message:
Hatch this egg by feeding it butter. It likes all kinds of butter, every kind. The best kind
Rumors abound as to why and who this is happening to. From multiple eggs being incubated to being on team Yellow.
One of the speculations is that it has something to do with potions or other items, where you can swipe over to them from the incubating screen.