What does the narrator mean by “a moment of temporary mental apparition”?

Sam and Bill are obviously swindlers, confidence men, who
specialize in cheating simple rustic people out of their money with various schemes.
Both men have cultivated big vocabularies in order to impress the yokels. They are
similar in this respect to the two rapscallions in Mark Twain's The Adventures
of Huckleberry Finn who call themselves The King and The Duke but who are
really only ignorant petty crooks. Both Sam and Bill use big words inappropriately.
These are called "malapropisms." What Sam the narrator is trying to say is that Bill
expressed the idea of kidnapping a child "during a moment of temporary
aberration." Part of O. Henry's reason for portraying these two
would-be kidnappers as men who are not as smart as they think they are is to explain how
they could have made so many mistakes and gotten themselves into so much
trouble.

In Hollywood parlance "The Ransom of Red Chief"
would be called "a busted caper story." There have been many films in which crooks plan
a crime (a "caper") carefully but things start going wrong because of unforeseen
circumstances. An excellent example of a "busted caper" film is
Fargo (1996), starring William H. Macy as the man who hires a
couple of incompetents to kidnap his wife so that he can collect a million dollars in
ransom from her wealthy father.

According to
Wikipedia:

readability="6.75">

The word malapropism comes
ultimately from the French mal à propos meaning "inappropriate" via
"Mrs. Malaprop", a character in the  href="http://en.wikipedia.org/wiki/Richard_Brinsley_Sheridan">Richard Brinsley
Sheridan comedy  href="http://en.wikipedia.org/wiki/The_Rivals">The Rivals (1775)
who habitually misused her
words.

In addition to
malapropisms, there are other misuses of language in the story. For example, Sam
says:

There
was a sylvan attitude of somnolent sleepiness pervading that section of the external
outward surface of Alabama that lay exposed to my
view.

The words "somnolent"
and "sleepiness" mean the same thing, as do "external" and
"outward."

A large part of the comedy in O. Henry's "The
Ransom of Red Chief" comes from the fact that the kidnap victim's father, whom they take
to be an ignorant country bumpkin, outsmarts the two city slickers. This sort of theme
has been a staple of American humor for many years.