None. They just let Marketing explain that "Dead Bulb" is a feature.
or
It takes two. One to change the bulb, and the other to kick the switch.
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Seven months old.
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The bartender offers him a warm smile and says, "For you, no charge".
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Because an undocumented worker has been living on his head for the past 2 decades!
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Finding a cabinet position for the thing on his head!
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One; after reflecting in the twilight on the merit of the previous bulb.
or