Everybody ever attending Gelfand's seminar in Moscow remembers that his jokes and stories inspired by the talks played a very prominent role there. It would be nice maybe to collect some of these stories.
For starters let me mention the well-known Koz'ma Prutkov's fable "Forget-me-nots and Footboards" translated into English and successfully used for the same didactic purposes by V.Drinfeld in his Geometric Langlands Seminar.
And here is another one that I heard from I.M. on numerous occasions. A man starts suspecting that his wife is having an affair, and hires a private investigator to check his suspicions. After a while the P.I. returns with a report: "I've followed your wife to a hotel. She was joined by a man, they kissed and entered a room together. I watched them from an apartment across the street. They kept kissing each other, then undressed, came to the bed, and turned off the lights, so I couldn't see what happened next." The man (with a deep disappointment): "Damn this uncertainty!"
Your contributions are welcome.