I've helped put easter eggs into sooo many products. Exhortations from management ("... firing offense") simply made us hide them much, much better.

One product I worked on (ahem, no names) we had written an easter egg and hooked it up and everything, then we got cold feet. Not because of any silly rules, but because we realized it truly would have been bad for the product and the company if the egg had caused something to go haywire. We looked at each other, then unanimously decided to remove it. Masking the true purpose of that check-in was actually much harder than hiding the egg to begin with. :-)