There's currently a heated debate among the Metal Gear Solid community as to whether Big Boss can canonically smell or not, because the implications massively change one scene in The Phantom Pain.
When you begin Metal Gear Solid 5: The Phantom Pain, you're prompted to enter your birthday. This isn't an age verification check - it's actually to prompt the scene just below, in which Diamond Dogs celebrate Venom Snake's birthday by rolling out a big birthday cake for him, accompanied by a cigar handed to him by Revolver Ocelot to mark the occasion.
