"Czech" Flag.

Here's a simple mistake that turned into diplomatic faux pas in Islamabad, Pakistan:

... the Prime Minister of the Czech Republic is visiting Islamabad, and the Capital’s PR people have adorned a number of (very) large banners to welcome him in the spirit of good hospitality. The only problem is that instead of putting the ‘Czech’ flags on the banners, they have ‘Check’ flags!

Link - Thanks Alex Feldstein!