Festivus is a holiday celebrated on December 23 as an alternative to participating in the pressures and commercialism of the Christmas holiday season. Originally a family tradition of a Seinfeld script writer, the holiday entered popular culture after it was made the focus of an episode in 1997. The holiday's celebration, as it was shown on Seinfeld, includes a Festivus dinner, an unadorned aluminum Festivus pole, practices such as the Airing of Grievances and Feats of Strength, and the labeling of easily explainable events as "Festivus miracles."

Here's a clip from the Festivus episode titled "The Strike."