Metal Gear Solid 5 celebrates your birthday, or technically, Big Boss's birthday with a party at your Mother Base. Obviously, don't watch the video if you don't want to see the moment spoiled.
When you boot up the game you're asked for your birth date and if you play on that day Kaz and Ocelot will be on hand to sign their very own rendition of a happy birthday song.
You'll need to play at least the first level for the event to trigger and there's an extra scene if you've recruited Quiet which you can check out below.
Metal Gear Solid 5: The Phantom Pain is available now on PC, PS3, PS4, Xbox 360, and Xbox One and by all accounts it is quite brilliant.