I guess I've been watching too much
Sci-Fi Channel, but it certainly seems like certain actors have pretty much made the rounds of science fiction (or fantasy) shows produced in the last 7 years or so. The top winner, I'd say, is Grace Park, but listed below are some of the more prolific actors and their current and past roles.
Grace ParkBattlestar Galactica (Athena/Boomer/Sharon)
The Dead Zone
Jake 2.0
Dark Angel
Kandyse McClureBattlestar Galactica (Dualla)
Smallville
Jake 2.0
Dark Angel
Aaron DouglasBattlestar Galactica (Chief Tyrol)
Smallville
Dark Angel
Nicki ClyneBattlestar Galactica (Cally)
Dark Angel
Jensen AcklesSupernatural (Dean Winchester)
Smallville
Dark Angel
Did
Battlestar Galactica just import every
Dark Angel bit player they could find? I could probably go on, but I think the point is made.