From the groaners listserv.

Dave moved to a new neighborhood much closer to his office. He was looking forward to a fifteen minute walk to work instead of the one hour commute he was used to. As he walked down his street he noticed through a window a woman hitting her child over the head with a loaf of bread. He found this somewhat strange but continued on his way.

The next day, the same thing. The woman was once again beating her son over the head with a loaf of bread. Dave was concerned, but continued on his way figuring it was none of his business. Every day for the next two weeks, Dave would pass the house and every day he’d see the woman hitting her son over the head with a loaf of bread.

Then one day as he passed by, he saw the woman hitting her son as usual, but this time with a cake. He couldn’t stand it any longer so he knocked on the door. The woman answered the door.

“Excuse me for disturbing you, ma’am,” he said politely, “but I recently moved to the neighborhood and I pass your house every morning on my way to work. I’ve noticed that every day you appear to be hitting your son on the head with a loaf of bread!”

“That’s right.”

“Every day you wallop him on the head with a loaf of bread, and yet this morning you were hitting him with a chocolate cake….?”

“Well, today is his birthday!”