When Ethan first appeared, did they know he was going to become evil? Or was this one of those "Locke was in a wheelchair" things.

BTW, my son's name is Ethan and we're terrified of him now. (:eek2:)

your line about your son is hilarious!!
my guess is that they knew generally of ethan's place in the development of the story, but they didn't know everything, eg, that he'd have a creepy lower-the-head-when-looking-at-claire sort of thing. some things even the writers can't anticipate...