[Spoiler alert! Arrancar arc]
I was curious about a pairing I've seen a few times between Orihime and Ulquiorra, which I suspected to be a case of Stockholm Syndrome, so I read all the Bleach chapters since Soul Society arc... and I realize the appeal.
Ulquiorra represents Nihilism, which initially struck me as a psychic deadness with dark circles around his eyes and marking that resembles tear-streaked eyeliner :-P And he has minimal facial expressions and minimal emotions. However, he's extremely perceptive and logical, kind of like L from Death Note... Serious resemblance :-P
There's always a tension between Ulquiorra's interaction with Orihime when she is kept captive at Aizen's palace. He never does more than what's necessary (e.g. gratuitous violence), and is generally civil. He does not understand why Core Crew (her school buddies) are coming to save her, although he seems genuinely curious about how this motivation arises. A bit like the Bicentennial Man robot. I can see how the Stockholm Syndrome (and a bit of Lima) comes about... especially as he turns to ash after battle w/ hollow Ichigo.
Oh and the Shinigami training academy is like Hogwarts + Quantico. =P