Quote Originally Posted by Crash
He didn't. Back in one of the earlier episodes he explained that he lost his body and was now stuck in the body of the cat. He went on to say that as a result of the animals smaller brain capacity the organization had to patch his mind into their sever system in order to keep his human level of intelligence in tact. Since at the end they cut him out while he was hacking through files he simply degraded to the intelligence of a cat over time.
That's the most reasonable explanation I've heard so far. Another theory I heard also mentions that it could be something to do with his wincing when he got cut from the server. But I though the intelligence degrading would have been more gradual. It seems like, for some reason, that Mao knew when it would happen. But it makes perfect sense never the less, especially considering he said: It's been fun with you guys. I actually prefer wet food to Kibble, so if a similar looking cat comes along......you know what to feed him.

I also liked how Yin gets a form when she sends her spectre. Really shows how she's "evolved" and isn't just some basic life form, but something unique.

Overall, loved this ending. Answers most mysteries, and the ones that aren't keep this series elusive, as it's always been. Though a little saddening, much better than Claymore, ending-wise at least.