Because they had so many knights.
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1,622. One to tell the original joke, and the rest to submit give some minor variation of it! For example:
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The same as a regular year, but with less calories.
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Because E.T. eventually went home!
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They both whine alot!
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Nearly unanswerable, since the one who tries to change it usually drops it, and the others call for a planning session.
or