1. So we found out in "Turn Back the Pendulum" that Yoruichi wasn't just the Head of the Secret Assasin Squad (or whatever they're called) but also Second Division Captain, and therefore a Shinigami. Okay, so, uhm, where's her zanpakuto? And, er, why can she change into a cat? Assuming she's not just a complete anomoly, my best guess is that her cat-form might be related to her zanpakuto. Possibly she's internalized her zanpakuto so completely that she has its powers, and has become her own weapon? (I almost hate to suggest that since it sounds exactly like what Kariya had done in the Filler From Hell Bounto Arc, but it's the only thing I can come up with.)
2. The Shihoin Clan: what's up with that? Why did Ukitake have the seal with the Shinoin crest on it? His bio says his family is minor nobility. Possibly Ukitake's family is a client of the Shihoin? Or maybe there's a close past history between Yoruichi, Ukitake and Shunsui? I add him because in Vol 17 when he grabs Ukitake and makes a run for it from the execution, he says "Can't you feel it? Another ally is here." meaning Yoruichi, of course. Also interesting is her dressing up Ichigo in a dashing cloak with a tentoken bearing her clan crest. Now, she says she did that because it gave Ichigo the ability to fly -- she seems to have some intriguing artifacts at her disposal -- and I'm also sure she did it as a slap in Byakuya's face, but I wonder if there's more to it? (A nod to Ichigo's possible noble/royal lineage, as I've heard suggested? Putting it right in front of Byakuya's face that "Oh yes, Bya-chan, you may not think so, but this kid is just as high-class as you; and you are going down." (I'm totally down with that, BTW. I'll never kick ass like Yoruichi, but that's exactly the sort of trick I'd pull.)
3. More on the Shihoin: My impression was that the Shihouin clan had fallen -- like the Shibas -- when Yoruichi fled, but something Soi Fon says in Vol 18 -- "if they find out you helped a ryoka, you'll be banished from the Four Great Noble Clans. The Shiba Clan has fallen as well." -- leaves that kind of up in the air. Is the Shihouin a fallen clan or not? It also begs the question -- just what did the Shiba Clan do to get banished? It also sounds like Soul Society is getting low on Four Great Noble Clans. Only three -- maybe even only two -- left as I count. Unless when one clan falls they replace with another?
Maybe this stuff has all been answered in interviews that I've never seen, or debated to death on forums that I don't follow, but since I enjoy speculation, discussion and the keen minds at bleachness, I thought I'd toss out these bones for chewing. Lots of meat left on them, it seems to me. ;-)
Discuss, discuss. I'll be back after