Confirmed: You actually can be dressed as Altair in MGS4
Konami have revealed that you will be able to unlock an Altair Assassin's Creed outfit for Snake in MGS4. It was seen in a http://www.youtube.com/watch?v=cxw91PSTRq8 earlier this year, but was presumed to be an April Fool's joke.
To quote: Snake running around MGS4 dressed as Altair, looking for all the world like it was actually in the game... so would it surprise you to hear that it wasn't really a gag? Yeah, that's right.
It was announced at the http://kotaku.com/5008810/presser-start today that MGS4 players will indeed be able to unlock an Assassin's Creed outfit for Snake (we won't tell you how), which were it not for the silver moustache and trademark cigarette would have you thinking Altair himself had time-travelled his way into the final Metal Gear title.