Japanese has some interesting phrases to it that at first hearing sound somewhat strange to the foreign ear. For example, when you present a gift to someone it's customary to say "tsumarani mono da kedo" which literally translates as "It's a boring thing but....". You have to wonder the origin of that one but it is the polite way to give something.
Another that is heard everyday on the train and follows the announcement of the station your train has just arrived at. As the passengers exit the carriage an announcement reminds them not to forget anything by saying "wasuremono wasurenaide kudasai" which means "please don't forget your forgotten things". Obvious if you think about it.
Probably my favourite though is the response as someone leaves the office in the evening. The departing party will start by announcing they're about to be rude and go home first "saki ni shitsurei shimasu" - "going first I'm about to do something impolite". To which the reply from those still at their desks will always be "o-tsukarasama" which pretty much means "Be tired!".
And don't even get me started on why a headache can have a headache....