What is ou manke yon fèy in Creole?

manke yon fèy (literally  missing a leaf) means the same thing as the English expression to have a screw loose, to not be in the right frame of mind

Ou manke yon fèy
You're crazy.
You're not thinking straight.
Haitian Creole ↔ English Reference, Look up Haitian Creole and English Words