My favorite tidbit of the series (but it's in Metal Gear Solid 3): in the torture scene where Volgin interrogates Snake in an attempt to discover who is the spy in his ranks, of all the persons present in the room (and if I got everything right from memory):

- Volgin is not an agent

- Snake is an agent (USA spy)

- The Boss is a double agent (Soviet/USA spy)

- Eva is a triple agent (USA/Soviet/Chinese spy)

- Ocelot is a quadruple agent (GRU/KGB/CIA/Philosophers spy)

And of course, after that Volgin then kills Granin thinking he was the spy, but he wasn't.