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).
or
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
Only one. But he'll leave a big puddle of spit on the floor underneath him.
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Because there's no one else to wag it for him.
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You go on ahead. I'll hang around for a while.
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Because E.T. eventually went home!
or