And it will only take you 15 minutes to unlock. SPOILER WARNING. READ THE (NOT VERY) GORY DETAILS IF YOU DARE.
First things first: If you play Far Cry 4 the way it's intended to be played (as, you know, a first-person shooter), it will take you much longer than 15 minutes. However, as a sort of joke alternate ending, Ubisoft's given players the option to wait around near the beginning of the game for Pagan Min to return to his snazzy villa after he takes you, Ajay Ghale, a young man who's returned to Kryat to scatter his mother's ashes, captive.
Normally this would be the part where you flee, rampage around, and get embroiled in the civil war at the heart of Far Cry 4's plot. However, if you simply sit there, "enjoying the crab rangoon" as Min says, for a little more than 10 minutes, he'll come back and be your BFF. Or at least, he'll give you a very personal history lesson and take you to a place where you can put your mother's ashes to rest.
After exiting the shrine where you've deposited dear old now-conveniently-travel-sized mum, you rejoin Min near his helicopter. He then quips, "Oh good. You feel better now? Get it out of your system? Maybe now we can finally shoot some goddamn guns." Then "Should I Stay Or Should I Go" by The Clash plays and the credits roll.
Kudos on the find, GameSpot.