False Friends - 祭

For people who know Chinese, you'll know the word 祭 is related to rites, rituals, sacrifices. It has not so positive connotations.

For people who know Japanese, you'll know the word 祭 is related to festivals. It has very positive connotations.

So if your colleague goes to Japan, buys back a banner with the word 祭 to hang as decoration in the office cubicle in an office with more Chinese than Japanese, maybe it's good to advice said colleague to take it down. XD