Three sisters are getting married but their parents are to poor to afford three separate weddings so they decide to have a joint wedding and get married at the same time. After the wedding they couldn't even afford a honeymoon and they had no place to stay so they stayed at the sisters parent's house.
That night the mother was walking from room to room to check on her newly wed daughters. She put her ear to her oldest daughter's room and heard laughing.
Then she walked to the middle daughter's room and heard screaming.
Finally, she walked to her youngest daughters' room and heard nothing.
So the next morning at breakfast she asked her oldest daughter why she heard laughing last night in her room, and her eldest daughter replied, "Mom, you told me when I was younger to laugh when I heard something funny."
She walked over to her middle daughter and asked her why she heard screaming in her room last night in her room, and the middle daughter replied "Mom, when I was little you told me to scream if I saw something scary."
Lastly, she asked her youngest daughter why she didn't hear anything in her room last night, and the young bride replied, "Mom, when I was younger you told me not to talk with my mouth full."