What would a lucky charm have to do with a chocolate bar? You would've known if you were in Japan or had read this news item on BBC. Japanese students have adopted Kit kat bars as a lucky charm resulting in enormous increase in the sales of these chocolate bars. The name actually resembles the Japanese expression - "kitto katsu" used by students to wish each other luck before exams and is translated roughly as: "I hope you will win."
Now I know what to do this Monday morning before I enter my examination hall - Get someone to buy me a Kit Kat!