1. *laughing* How about "Waaaaa!" It comes from 哇 and could be used for a surprised cry. The generic Aaaaaaaa works, too. As for Japanese ... er. XD I suppose you could just use any noise. "Oi!" seems to be the best one for the situation.

2. Ah, totally missed the "fake" connotations! T_T Sorry. "Ni yao jia de zuo shen me? Zhen de zai zhe li!" (Why do you want the fake? The real thing is here!)

3. XD Up to you!