Only one. But he'll leave a big puddle of spit on the floor underneath him.
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Because an undocumented worker has been living on his head for the past 2 decades!
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they never get old!
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Billllyuns and billllyuns. Light bulbs are part of the interstellar "goo" that pervades our universe; they are star stuff.
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Seven. One to install the new bulb and six to figure out what to do with the old one for the next 10,000 years.
or