As Seinfeld fans know, the characters were shallow, self-obsessed, largely amoral and generally unlikable people. The show’s genius was that they combined to produce some of the funniest moments in television (“sponge-worthy,” “master of your domain,” etc.).
A benefit of its nine season run was that the characters became well-developed; none more so that George. His parents were regulars, and the many events from his childhood that turned him into a stingy, deceitful and neurotic adult were recounted. The most classic is in the above clip as it explains the story of Festivus.
Festivus is a holiday invented by George’s father and celebrated on December 23. Its traditions include the Festivus pole, the airing of grievances and the feats of strength. Through the magic of YouTube, all of the Festivus parts of the episode “The Strike” are in the above clip. Wikipedia has more Festivus details for the curious.
Bonus link: for more twisted holiday humor, don’t overlook South Park’s The Spirit of Christmas (now back on YouTube). This not safe for work or children precursor to the TV show is as humorous as it is irreverent. Thanks to SFist for the reminders.