In the current day and age, hidden secrets and easter eggs are very few and far between. Chances are that a couple weeks after a game's launch there will already be in-depth analyses, full guides and expansive lists chronicling the obscure details that you most likely missed on your initial playthrough. Such is the age of the internet.
So, when developers manage to bury something for years on end in their games, it really is nothing to scoff at. Being able to trick data-miners, codebreakers and intrepid fans is something of a talent and one that is severely underrated considering the prevalence of online researchers.
All of which makes the things on this list all the more impressive, as more often than not, when a secret is hidden very well, it can take years, even decades, to uncover, meaning that titles that were long thought to have been mastered, still have hidden tricks to be revealed.
It also makes you spare a thought as to what else remains hidden to this day. Perhaps in years to come, the games we think to be so over-exposed will surprise us with some hidden detail that even the full force of the internet couldn't find.