How are stock characters used in The Importance of Being Earnest by Oscar Wilde?

We might read Gwendolyn as a soubrette: a female character who is vain and flirtatious.  Though she is somewhat mischievous and likes to hear and spread gossip, the soubrette is ultimately light-hearted.  Gwendolyn falls in "love" with Jack, but it seems that the name she believes is his––Ernest––plays a big part in her feelings.  It also appears as though her mother's disapproval of Gwendolyn's feelings for Jack/Ernest go a long way in prompting her...

We might read Gwendolyn as a soubrette: a female character who is vain and flirtatious.  Though she is somewhat mischievous and likes to hear and spread gossip, the soubrette is ultimately light-hearted.  Gwendolyn falls in "love" with Jack, but it seems that the name she believes is his––Ernest––plays a big part in her feelings.  It also appears as though her mother's disapproval of Gwendolyn's feelings for Jack/Ernest go a long way in prompting her to feel them even more deeply; in other words, she loves him for his name and because her mother doesn't like him.  Her initial interaction with Cecily shows her vanity and gossipy side, but, in the end, she has a sense of humor and a good heart.

We could read Cecily as an ingenue: another young female character who is completely wholesome and sweet.  Although Cecily can give as good as she gets in terms of her interaction with Gwendolyn, she is young and sweet and very romantic.  She's concocted this entire fantasy relationship with Jack's "brother," Ernest, and when he seems to show up at the house, she is already head over heels in "love" with him as a result of his name (which isn't really his) and his bad-boy nature (which is somewhat more truthful).  

Using stock characters really increases the humor in the play, because we recognize these characters as types.  They aren't characters with whom we are likely to empathize, because they are not really three-dimensional or well-developed; they are also quite static––they don't learn lessons or grow.  They are almost all at least a little bit immoral in a way that would not be funny at all in real life, but because we see them for what they are, we can laugh at their behavior and their really terrible choices.