Robanukah

Robanukah was only mentioned in Fear of a Bot Planet and is supposely the "holiest two weeks on the robot calendar." It was invented by Bender Bending Rodriguez as an excuse to skip work. It is celebrated one month after Robomadan, which itself is celebrated one month after Robonza (which is a holiday that tributes his ancestral prototypes and is celebrated by drinking contests), which were also invented by Bender.

A story dedicated to Robanukah will appear in episode 6ACV13 of season 6, meaning that rather than having been invented by Bender he may have merely reused it.

Trivia

 * Robanukah is very similar to Chanukah, including the music and 8 candles, even though it lasts for 2 weeks. Other traditions include carving toxic waste barrows like jack-o-lanterns, cutting robots out of paper and doing the "robot" break-dance.