"Easter Eggs," little programs hidden inside other programs, have long been part of the programming universe, most often as jokes or ways to sign otherwise uncredited work for those able to find them. If you want to add an innocuous Easter Egg to your application for that purpose, just use the Demo Account Field to let the review team know the unlocking steps. Apple considers this information confidential and will not reveal those steps or their existence.
On the other hand, not telling the review team about an Easter Egg in your code in order to circumvent the review process is not allowed. When its existence becomes known, as it inevitably will, our first step will be to remove the offending application from the App Store. Read more app submission tips