The 30 Rock episode "Leap Day" transforms leap day (February 29) from non-holiday into full-blown, commercialized, Christmas-esque bash with established traditions and traditional holiday characters. Liz is the only character who had never previously known Leap Day was such a big deal. It’s the fourth most memorable fictional holiday ever.
Festivus is a secular holiday, normally celebrated on December 23rd. It is mainly meant as an alternative to the pressures and commercializtion of the Christmas season. However, it has also become a day to celebrate the ever-lasting comedy of the 1990s television show Seinfeld. Festivus was a holiday featured in the Season 9 Seinfeld episode "The Strike", which first aired on December 18, 1997. Since then, many people have been inspired by this zany, offbeat Seinfeld holiday and now celebrate Festivus as any other holiday.
The usual holiday tradition of a tree is manifested in an unadorned aluminum pole, which is in direct contrast to normal holiday materialism. Those attending Festivus may also participate in the "Airing of Grievances" which is an opportunity to tell others how they have disappointed you in the past year, followed by a Festivus dinner (a platter of meatloaf on a pile of lettuce), and then completed by the "Feats of Strength" where the head of the household must be pinned. All of these traditions are based upon the events in the Seinfeld episode. It’s THE most memorable fictional holiday ever!