An 80-year-old couple was worried because they kept forgetting things all the time. The doctor assured them there was nothing seriously wrong except old age, and suggested they carry a notebook and write things down so they wouldn't forget.
Several days later, the old man got up to go to the kitchen. His wife said, "Dear, get me a bowl of ice cream while you're up." "Okay," he said. "...and put some chocolate syrup on it and a few cherries, too," she added. "You'd better write all this down." "I won't forget!" he said.
Twenty minutes later he came back into the room and handed his wife a plate of scrambled eggs and bacon. She glared at him. "Now, I told you to write it down! I knew you'd forget." "What did I forget?" he asked. She replied, "My toast!"