Though the anime genre comes in cartoon form, plenty of deep anime tackles subjects that cannot be solved in a single Toonami sitting. So what sets this kind of cerebral anime apart from the usual fare? Anime that makes you think raises serious moral and philosophical questions to make you think, nothing as simple as mecha fights or fan-service. In many cases, smart anime utilizes outlandish supernatural and sci-fi elements to address real-life-issues of morality, justice, and philosophy. Godlike schoolgirls and bionic alchemists may not appear to be gurus of wisdom, but you'd be surprised how adult these anime series can be.
Don't worry, though, because these series aren't just relentless intellectualizing - that would be boring. Though Death Note tackles serious issues about being a moral arbiter, it's also an anime with sakujo-gasms and jokes about cake. That being said, anime for smart people gets even more fun when you're stoned: the visuals look better, and you gain new perspective. Rather than be daunted by anime for smart people, instead try to sit down and see what you can learn from them. In fact, the intellectualization in these deep anime below led to some of them to be declared the best anime of all time.