Perhaps the most famous and most recognized Tomism (see "Tomism"), the term is used as a general insult.
Tom K. would speak of another
person as having "the I.Q. of a peanut butter sandwich". It is believed that
Tom did not originate the phrase, however. In recent times, the phrase has been combined with "without the jelly" on the end- supposedly to indicate that a peanut butter sandwich WITH jelly has somehow a measurably higher I.Q. Go figure.