Why doesnt ककाशी take off his mask

Because Guy glued it to his face in the middle of the night with quick-dry super glue. ._.

Hehehe XP

Actually, I think it's to hide his emotions because he follows the ninja guide lines and rules pretty closely.. *shrug*

It is probably because of his father, Sakumo. His father brought dishonor to his family and committed suicide. ककाशी must wear a mask over his face to keep from reminding everyone of his father's disgrace to the Hatake family.

when did he do that ????????????
what episode it happen ?????