Similar thing happened to me. I started watching the first few episodes back when it first aired, thought "Hey, this isn't bad for a kids' show," but it didn't hook me in and I promptly forgot about it. Then a few months ago, I saw the ads for the third season and thought, "OMG, this got seriously dark. I have to know what happened to make it this way", and watched a couple of the later episodes. And I started kicking myself because holy crap, it was good. Then I devoured the rest of the show online.

There is one place on LJ you can go--atla_unspoiled. I haven't joined yet, but I plan to in case the withdrawal is too much.