This is my first time posting on this topic so I'll just spit out everything I have to say.
I recently re-watched some older episodes back when Akai was 'alive' and something occured to me. Since Akai said he dated Akemi(?)(I can't remember Haibara's sister's name....) he said that it'd be best if they didn't meet just yet cuz of Akemi dying and everything:
Kogoro's not himself. I'm thinking he's asleep in a toilet stall somewhere at the train station. As for who is disguising as Kogoro....I don't have the slightest idea....
And has anyone noticed that some of the train people seem to be acting a little....flustered? Maybe something'll come out of it.
Also, I had this funny theory for about 5 seconds today while watching episode 557 that Sera was Amuro in disguise (since he hasn't appeared yet) or vice versa with Sera disguised as Amuro (after he shows up)...then I remembered that they were in separate places at the same time in chapter 817....lol nope. but I still think Sera's a guy in disguise. No girl is that flat-chested.
and with everyone's theories on this thread...wouldn't it be funny/horrible if Aoyama-san threw in a curveball and destroyed all those theories?