There was a Scottishman, an Englishman and an Irishman and they were on the run from the Nazis.
They run into an alleyway and hide inside three large sacks.
A Nazi officer, upon finding the three suspicious looking sacks, kicks the first one. The Scottishman inside barks like a dog, and the Nazi continues.
He kicks the second sack, and the Englishman meows like a cat. The officer, shrugged his shoulders, thinking that it was odd to have two sacks of animals in an alleyway, but continued to the third sack just the same.
He gave the third sack a swift boot on the side, to which the Irishman responds with a huge, bellowing "potatoes"