First Michelle Forbes as Helena Cain, then Nana Visitor as Emily (episode Faith). Why interesting? Forbes played Ensign Ro Laren in Star Trek: The Next Generation, and a was offered a role in Deep Space 9. Forbes declined and and Visitor was cast as Major Kira Nerys in her place.

The episode of Star Trek Voyager entitled Q and the Grey there are some nice scenes based on the US Civil War. I was most enraged to see the Confederates running around with breachloading Trapdoor Springfields that weren't availalbe until after the war. I'm sure this was done for the benefit of certain tribes of geek.