None. They will never find a bulb that burns as brightly as the old one.
or
Just one, but he/she will spend hours checking for technical problems.
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Because it would fall over if it lifted the other one.
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Because he has such yuuuuge fans!
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When it came time to pay, the skunk didn't have a scent, the deer didn't have a buck so they put the meal on the duck's bill.
or