Who was That?

After putting her children to bed, a mother changed into old slacks and a droopy blouse and proceeded to wash her hair. As she heard the children getting more and more rambunctious, her patience grew thin. At last she threw a towel around her head & stormed into their room, putting them back to bed with stern warnings. As she left the room, she heard her three-year-old say with a trembling voice, "Who was that?"