My last project had 800 people on it and little things were added pretty much all over the place without the art directors ever knowing - even us as programmers

My last project had 800 people on it and little things were added pretty much all over the place without the art directors ever knowing - even us as programmers shipped some programmer art that definitely wasn't meant to be there but it got "accidentally" left in the game files and shipped. And then there is a whole category of "official" easter eggs that obviously get approved by creative directors and are meant to be there for players to eventually find.