I just thought of what I consider the biggest plothole in the whole game, which I hope any of you guys prove me wrong and I just oversee'd something, but anyway, here it goes:
So when the Ground Zeroes incident happened and Kaz, Big Boss and the Medic crashed with the helicopter, Kaz could see Big Boss entering in the coma, then asking about the status of the third soldier, on which the medic replies "He has some shrnapel stuck in his head".
Fast-forward nine years, and Kaz gets rescued by a Big Boss who happens to have shranpel in his head.
How did he not noticed it? How come he just didn't realize who he was in that instant, or when he got to Mother Base or anywhere after that? Why did he only realized after Ocelot tells him once the events are all pretty much done? It's almost impossible to ignore the horn, mind you.
Something else I can't get is that, even with suggestion, how come this "medic" ends up being as skilled as BB after 9 years in coma, but whatever I guess.