it's hard to tell from an online listing, but assume fake if the seller is from china
if you have a cart in hand, you might run into a strange save file error message (kind of like the dead battery one from gen 3) every time you boot up. most fakes i've seen have a hard time connecting to authentic copies. worst gen 3 fake i've seen would lose its save data if it communicated with a gen 4 game in dual slot mode
