Two. One to change the bulb, and one to write a song about how good the old light bulb was.
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None. The darkness will cause the bulb to change by itself.
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Only one, but it may take upwards of five years for him to get it done.
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None. Real Men aren't afraid of the dark.
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1,000,001: One to change the bulb and 1,000,000 to rebuild civilization to the point where they need light bulbs again.
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Five: one to handle the bulb and four to contemplate how David Sanborn would've done it.
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Twenty. One to hold the bulb, two to turn the ladder, and 17 to be on the guest list.
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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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Three, but they're really only one.
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Twenty. One to hold the bulb, two to turn the ladder, and seventeen on the guest list.
or