A mermaid! With shells for bra cups! Say what you like about Kimmy, at least she knows how to work her shape like nobody else and hasn't used Halloween as an excuse to dress like a prostitute (at least, not this year).
Kanye went as a sailor, I think. He wore a navy suit jacket with striped tee - does that constitute sailor?
She was hosting the Halloween party for Midori, hence all the green, and word is that Kanye loved the blonde locks on her.