First of all, japanese wannabe means a person that tries to be a japanese. They will try to speak some japanese when they see japanese, or even try to show it off to some of their friends.
Japanese Wannabe A : Watashiwa Yukari Chiuzibai!!
Japanese : Kuso!! Go and learn ur own language properly before u learn japanese buddy.
Japanese Wannabe B : Hello, I am from Japan (actually from china or some other asian countries) Nice to meet u all.. Kawaii people!
Japanese Wannabe C : Lets take some pics!! ( posing in a very ridiculous face that he/she thinks is cute )