Best explained by Frodo Baggins to Gandalf about Bilbo’s 111th birthday.
"Half the Shire's been invited. And the rest of them are turning up anyway."

Often happens at weddings and teenage/frat parties or events in small towns. What happens is when you invite your “A List” of family and friends half say they are not coming. So you send out your “B list” to give them a chance to come and hopefully keep the minimum number of people you set out to invite. However what can happen instead is that the people who said they weren’t coming come and even brings guests as well. Because of the majority of people moving in with each other instead of getting married marriage has become an "event".
Mother of the bride: "Hey was that the Andersons? I thought the invite said that they couldn't bring their kids. And who is that?"

Maid of honor"Its the Shire effect mom."
by thehostesswiththemost-est December 4, 2011
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