What effect does humour have in the play Pygmalion by GB Shaw?

In at least
some instances, the humor in  is directed against the supercilious
Professor Higgins and his social class that are so impressed with appearances and place so much
value upon how one speaks, dresses, and acts when they are so easily deceived by Eliza as she
performs correctly. Also, a couple of instances of humor illustrate that although Eliza is
well-trained to appear as if from the upper class, she does not know how to think and to react
as a gentlewoman, so she commits some rather humorous faux pas. So,
Professor Higgins can not really take a human being and change her into a quite different
human being by creating a new speech for her.

When, for instance, Professor
Higgins visits his mother and asks permission to introduce Eliza, she makes an impression
"of remarkable distinction" and when ask if it will rain, answers with pedantic
correctness of pronunciation and :

LIZA The shallow
depression in the west of these islands is likely to move slowly in an easterly direction. There
are no indications of any great change in the barometrical situation.

However, the conversation takes an ironic turn as Freddy thinks she
is parodying those that consider the weather of more importance than it deserves when she
replies in a similar manner a second time; he laughs, telling Liza she is "awfully
funny!"

When Mrs. Eynsford Hill remarks that she does not want the
weather to turn cold; she adds that there is much influenza around and spreads through
families. 

LIZA My aunt died of influenza: so they
said.
MRS HILL [clicks her tongue
sympathetically]!!!
LIZA [in the same tragic tone] But
it's my belief they done the old woman in
MRS. HIGGINS [puzzled]
Done her in?
LIZA Y-e-e-e-e-s, Lord love you!...They all thought she was dead; but my
father he kept ladling gin down her throat til she came to so sudden that she bit the bowl off
the spoon....What call would a woman with that strength in her have to die of
influenza?

In addition to the humor of Liza's ingenuous
failure of falling out of her pretentious role, Shaw satirizes the upper class of the Victorian
Age as Freddy delights in her language, believing it the latest "small talk" and Clara
Hill leaves after repeating "Such bloody nonsense!" [Bloody means
By our Lady and constitutes swearing] because Liza says it and the party believes she is using
the latest form of fashionable talk.