Weinberg's Law of Twins states that most of the time, no matter how much effort one expends, no event of any great significance will result. Weinberg's Law of Twins Inverted states that occasionally, particularly when one isn't expecting it, a significant event occurs. The law was invented by Gerry Weinberg in his book The Secrets of Consulting ISBN 0932633013, in which he explains the rather arcane name of this law.

Weinberg reported that he was on a bus in New York when a mother with six small children got in and asked the driver what the fare was. The driver said that it was one dollar, but that children under five went free. The woman put one dollar in the coin slot. The driver asked "Do you mean to tell me that all your children are under five years old?" The woman explained that she had three sets of twins. The driver asked "Do you always have twins?" to which the woman replied, "No, most of the time nothing happens at all."