|Season Two's cast.|
I suppose these prologues are a little bit redundant now, but there's no problem with a little bit of redundancy here or there. Lost's core focus shifted a great deal between the first and second seasons, with the character-based groundwork that Season One layed down allowing the mythos of the show to take a much more active role, as well as facilitating the introduction of a number of new cast members, the majority of which unfortunately didn't last very long past it.
Season Two introduces the Dharma Initiative, one of the show's biggest mythos points and the damn setting for most of Season Five. It also thus introduces Desmond, who is awesome. This all arrives with the opening of the Hatch to reveal the Swan, a Dharma Initiative station whose fashioned interior and mysterious contents form the backbone for a lot of the season, and help to define it with its own identity. Personally, I love the set and everything that goes with it, and thus its destruction at the end of the season is just heartbreaking for me on a number of levels.
Elsewhere we have Season Two's unique look at the Tailies, the survivors of the plane's Tail Section who feature a host of interesting characters, the best being Ana-Lucia and Eko. Ana-Lucia is one of the best-written female characters I think I've ever seen in US TV, and despite her haters (of which she has many for some unfathomable reason), I really love her. Mr. Eko is one of my favourite LOST characters, due to the sheer complexity behind him and his badass exterior that hides a tragic and desperate past. His best moment comes at the beginning of the next season, but Season Two gives him plenty of memorable stuff to do as well.
We're in the big leagues now, boys and girls. Get excited.