Only one. But he'll leave a big puddle of spit on the floor underneath him.
or
......... one jar.
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They keep dropping their trunks.
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Clerk: "Yes, sir. What size does your alligator wear?"
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Neither, they all burn shorter.
or
First they have to agree on which is better; the analog bulb or a digital bulb.
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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