When I was young in Poland I met the great mathematician Waclaw Sierpinski. He was old already then and rather absent-minded. Once he had to move to a new place for some reason. His wife didn't trust him very much, so once they were down on the street waiting with all their things, she said: "Now, you stand here and watch our ten trunks, while I go and get a taxi."
She went off and left him there, eyes somewhat glazed and humming absently. Some minutes later she returned, presumably having called for a taxi.
Said Mr. Sierpinski (possibly with a glint in his eye): "I thought you said there were ten trunks, but I've only counted to nine."
"No, they're TEN!"
"No, count them: 0, 1, 2, 3, ..."