I like the solution to the variant of the Knights and Knaves problem in Every Man For Himself And God Against All by Werner Herzog. To determine the liar, Kasp

I like the solution to the variant of the Knights and Knaves problem in Every Man For Himself And God Against All by Werner Herzog. To determine the liar, Kaspar Hauser asks both people -- the liar and the truth teller -- if they are a tree frog.