Falling Skies just aired their Season 2 finale on Sunday, and they’re back to work this week in Vancouver for Season 3. Which would seem a bit harsh if we didn’t know they finished shooting Season 2 months ago. We lost some great cast members by the end of the season – farewell Mpho Koaho and Peter Shinkoda – but we now know about three new cast members.

Deadline reports that our favorite former member of the Dead Poets Society and Princeton Plainsboro oncologist Robert Sean Leonard will be joining the fray as an “obsessive but gifted” scientist who runs the power grid for Charleston, and whose pets earn him the nickname “The Rat King.” He’ll be on in a 5-episode arc.

Also in for 5 episodes will be Gloria Reuben, who once worked with Falling Skies star Noah Wyle in the same hospital – ahem – Emergency Room, and will be playing Marina Perlata, an aide to Noah Wyle‘s Tom Mason.

Finally, EW is reporting that Doug Jones, the Angel of Death in the Hellboy movies and the Silver Surfer in Fantastic Four: Rise of the Silver Surfer, will be playing that very interesting new alien we saw at the end of the Season 2 finale, in Season 3. Will the newbies be good? Bad? Horrifyingly bad? It’s a pretty safe bet they won’t be neutral.

Speaking of that Season 2 finale, here’s a behind the scenes featurette about some of those unanswered questions:

Falling Skies – Unanswered Questions – A More Perfect Union
[youtube]http://www.youtube.com/watch?v=Z26cKt5Q-ac&hd=1[/youtube]

Falling Skies Season 3, starring Noah Wyle, Moon Bloodgood, and Will Patton, will premiere in 2013 on TNT.