Back in the Middle Ages, on erev Pesach, Sir Lancelot gathered his men at the encampment.
"My knights!" he exclaimed. "It is a great honor that in two days time, King Arthur himself will be coming all the way from Camelot to visit us. We must make ready in haste! Shine your armor! Groom your horse!"
In the background, one man raised his hand. "But Lancelot," Yussel cried. "Tomorrow night begins the Passover holiday, and I will be unable to do anything to prepare for his arrival. I've got chametz to clean out, and a seder to attend."
Lancelot was unmoved. "He is coming, and you will be ready."
And so, two days later, a procession of magnificent horses led King Arthur to the encampment.
There they were, Lancelot's men -- their horses well-groomed and outfitted for a royal visit, the men clean-shaven, their armor polished so extensively that you could see your reflection off them.
All of them, that is, except one. When King Arthur reached the end of the line, there was Yussel, his horse mangy and unkempt, his armor dinged and rusty.
King Arthur turned to Lancelot, and asked: Mah nishtana halaila hazeh mikol halelot?
Via Bernie Kaplan. Possibly, just possibly apocryphal.