Rootbeer.
or
Climb up a tree and act like a nut
or
Because an undocumented worker has been living on his head for the past 2 decades!
or
They turn from notating nuclear spins to notating unclear puns.
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His powder puff is on the wrong end.
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Just one, but he/she will spend hours checking for technical problems.
or
A centipede with a wooden leg.
or