I was ruminating as to why the Fifth Cylon didn’t show up at the same time as the other four. Possible answer: because he or she wasn’t on Galactica at the time.
That might mean the Fifth Cylon is elsewhere in the fleet. Or it might mean it’s someone we’ve never met. But the third possibility is that it’s someone who was previously on the ship but died – only to be resurrected in some Fiver tank somewhere.
And in that case it really needs to be Billy Keikeya.
And he really needs to be the Imperious frakkin’ Leader.
You don’t think it is Starbuck?
Ha, an “Imperious Leader” would be a hilarious, put possibly not unwelcome, addition to the series.
See the link above as to why it’s almost certainly not Starbuck.
What if it were someone who died before the show started? Like Adama’s other son? We know that persons from that period are open to be Cylons, as Tigh was a Cylon.