it's as sure as eggs are eggs it means definitely
Because if it were a ninja, you'd be dead.
The quote, " as sure as eggs" as from To Kill A Mockingbird, by Harper Lee can mean many different things. But the most clear definition is that it's "somthing that you say when you are certain about...
It is an old British and Australian saying.
Actualy the answer is no beacuase if you slowly take apart a shell it'll have plastic see through white stuff and that's the stuff that holds the egg