Quite possibly the funniest line ever by Leonard Nimoy
in Star Trek:TOS
. The reason is that he was, in fact, singing
the words whilst playing his 'Vulcan Lyre' and, as we now know, Leonard Nimoy (and hence, Spock) cannot
The episode was "Plato's Stepchildren", and first aired November 22nd, 1968.
Note: Many thanks to furby100, who caught me referencing a COMPLETELY WRONG episode and corrected me!