My Dad writes, “If Derb can publish his bicycle pump ‘joke’ in the Corner, with nothing to do with math, then I think you should display the Lithuanian Yiddish herring joke, one of the oldest I know, and for some reason I think it would appeal to a professor of mathematics, or at the least a professor of logic:
“What’s green, hangs on a wall, and whistles?”
“I don’t know.”
“A herring.”
“But a herring isn’t green.”
“So, you paint it green.”
“But a herring doesn’t hang on a wall.”
“So, you hang it on a wall.”
“But a herring doesn’t whistle.”
“So, it doesn’t whistle.”