It was accidental. Eggs are there on purpose. It is symbolism, foreshadowing, or any other literary technique like this. Storytellers use these all the time to tell a good story, and they certainly don't count as Eggs. It fits in with the context of the work in question.
Eggs stand out as being different from their surroundings.
It is a plot inconsistency, or just some wierdness you can't explain. It is interesting background information, but doesn't stand out in the work in question at all. Sometimes examples speak louder than rules. Here are some examples of genuine, indisputable Easter Eggs, and you should use them to guide your gut feeling about what is or isn't a true Easter Egg. Yes, my submission really IS an Easter Egg.