i wondered that too. a friend told me about it earlier today and i was like "oh cool" and then "wait, what?" immediately after.
LOL, you think bleach is a mature anime?! its pretty damn childish compared to lets say cowboy bebop, akira, code geuss, gun grave, gilgamesh, golgo 13 etc... Bleach is pretty much naruto in a different setting, just with better animation... as for that show, it seems really messed up... especially since all the bad guys were camels and i didnt see a single cat, so wtf is cat **** one?!
My friend linked me this the other day. 'in the manga the storyline is placed in vietnam where the vietnamese were cats The russians were bears, the australians koalas etc.' That was his explanation for it. I also recommend Genshiken as an Anime, not much violence but full of lols =]
Nobody's mentioned Death Note, I notice. It seems for every one person willing to call it "mature", there are twenty ready to call it "emo", which seems unfair. I think death note is the most mature anime I've seen so far (feature length films like Akira excluded) - though still not quite Jack Bauer.
death note was excellent, i don't think I've ever seen a sociopath that well represented on the screen, that kid was major twisted!