The Dog the Didn't Bark
Bulgars are still sensitive about the famous UK umbrella incident (poison brolly in enemy buttocks) even though it was long ago in the "cold war era."
Evidence of persistent collective embarrassment: there is a statue of Charlie Chaplin outside the House of Humor and Satire in Gabrovo, Bulgaria, the only known depiction of Chaplin in the world without an umbrella.
http://www.philposner.com/idolclass/bulg.htm