I know that there is whole other page of forums that this should go under, but oh well. In this months issue of XBN, Alex Seropian states "I don't thin you ever find that out, but it's the same character... God, we've never said that before, but it's completely obvious. Cortana isn't in Marathon, but there are three A.I.'s in there that came from the same stylistic story line." So there it is directly from one of the lead developers. Marathon and Halo are connected. The last question is how will this play into the Halo story?