I know I have told this one before:
When going out to dinner with the family, my father would never order dessert for himself. While everyone else would be eating their dessert, he would look intently from one to the other at every bite until one of us would crack and say, "Oh, here, just take it." The first time we went to a restaurant with Mom and Pop, Pop tried it on DH. DH was oblivious, and, in spite of my father watching every bite he took, finished his dessert. DH later asked me why Pop was staring at him.
We never did break Pop of this habit, but he never tried it again with DH.