Seven. One to change it and the other six to sing about how good the old one was.
or
First he lies on one side, then he lies on the other.
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One's a spineless, poisonous blob. The other is a form of sea life.
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In a hambulance.
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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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50. One to screw in the light bulb and the remaining 49 to guard him .
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I wuv you watts and watts.
or