It all starts with a yellow rubber duck.
In MGS2, you find it in one of the air pockets [while getting/rescuing Emma]
In Castlevania: Aria of Sorrow there is a room with Succubus and Lilith enemies
[sorry for the small pic, its there.]
So what I'm saying here is, there was a good chance that Konami was hinting at a Kojima Castlevania years before it was even announced [This game was Lords of Shadow].
ITT: I can't look at Konami the same way again.