In November, Assassin's Creed IV writer Darby McDevitt put out a challenge on Twitter:
P.S. #AC4BlackFlag fans. There is an ultra-hidden John from I.T. Easter egg somewhere in the game. Someone tweet me if you find it.
— Darby McDevitt (@DarbyMcDevitt) November 7, 2013
Three months later, someone's finally done it. YouTuber Kosappi Uni found the hidden message buried in the sound files of Ubisoft's pirate game, and posted it in a video (embedded above). It's strange, and meta, and kind of funny, especially if you've beaten the game and learned more about John from IT. (For further, spoiler-filled reading on John, check out the Assassin's Creed wiki.)
Really, it's amazing, in today's world, that McDevitt and his team managed to keep an easter egg hidden for this long. Good work, guys and gals.