I was hopping into a cave near my place the other day in the mood for some spelunking when a horde of zombies of all kinds greeted me... ALL of them were holding eggs! I had 17 fresh eggs in my inventory when I was done clicking with my sword in panic.
Sadly I was too overwhelmed and busy laughing at the same time to take a picture >.<
Sounds like one of thoes episodes where a few chickens have been in a loaded chunk 'eggin'' it out and zombies pick them up and never despawn, Have your place been laggy lately? Good you found them before they overtook your cave, you might want to hunt the eggmachine down.