Dan O'Keefe, one of the writers for Seinfeld, invented the idea of Festivus with his family. Here is the background...
Linked from http://www.whatisfestivus.com/
What is Festivus... It's for the Rest of Us.
Festivus is a nondenominational holiday that is celebrated on December 23rd. The TV show Seinfeld helped popularize this holiday. Dan O'Keefe a writer on Seinfeld father discovered the holiday in a book published in 1966. The O'Keefe family celebrated the holiday for years. Then...Read Full Story
Festivus is a nondenominational holiday featured in the plot of "The Strike" episode of Seinfeld. Now many people celebrate Festivus out of respect for the show!