Two. One to hold the bulb and the other to rotate the planet.
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A stick.
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Two. One to take out the bulb and drop it, and the other to try and sell it before it crashes (knowing that it's already burned out).
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50. One to screw in the light bulb and the remaining 49 to guard him .
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Someone stepped on its mouse.
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Only one, but it sure takes a shitload of light bulbs!
or