It was at a party and the host was getting worried because there were too many people and not enough refreshments.
She was sure that not all of these people had been invited but didn't know how to tell which ones were the crashers. Then her husband got an idea....
He turned to the crowd of guests and said "Will everyone from the bride's side of the family stand up please?" About twenty people stood.
Then he asked " Will everyone from the groom's side of the family stand up as well?" About twenty five people stood up.
Then he smiled and said, 'Will everyone who stood please leave. This is a birthday party.'