Polish jokes here
And an attempt at analysis from Slate, March 27, 2014 "The Humor Code. Every Culture Has a Polish Joke" here.
"For the past several decades, British sociologist and preeminent humor scholar Christie Davies has been collecting examples of an odd phenomenon: Nearly every culture has its own version of the Polish joke. That is, every country likes to make fun of people who’ve been labeled as simpletons and, often, outsiders."