There are a number of characters ridiculed in Sense and Sensibility. This means in turn that the social-cultural types upon whom Austen was patterning them were also being ridiculed through their representative characters. The primary characters being ridiculed are Marianne and Willoughby--though lovingly so. The secondary characters being ridiculed are Sir and Lady Middleton, certainly Lucy, Robert Ferrars, Mrs. Ferrars, John and Fanny Dashwood, Mrs. Jennings, Lucy's sister Anne, and Miss Sophie Grey--although, Miss Grey has such serious flaws, it is hard to apply humorous ridicule to her.
To illustrate the subtle ridicule that Austen affords Marianne and Willoughby, when they have their first visit, Marianne and he cover every "important" topic of conversation from music to dancing to poets Cowper, Scott and Pope to authors to favorite passages within books. Willoughby's dissenting opinions hold out only until the
brightness of [Marianne's] eyes could be displayed. [Willoughby] acquiesced in all her decisions, caught all her enthusiasm.
Elinor contributes to the sense of gentle ridicule (after all, we do like Marianne, and there is critical debate over who is meant to be the heroine: Elinor or Marianne) when she playfully mocks Marianne about the speed with which she and Willoughby raced through discourse on so many topics (and managed to come out in agreement on all):
You will soon have exhausted each favourite topic. Another meeting will suffice to explain his sentiments on picturesque beauty, and second marriages, and then you can have nothing farther to ask --
Austen is ridiculing and showing the folly of "sensibility," which is the hyper-emotionalism typifying the romanticism of the Romantic period, which is the "sensibility" that Marianne and Willoughby display in such abundance. In the minor characters, Austen also ridicules vanity (Lady Middleton); manipulation (Lucy); empty, grasping love relationships (Lucy and Willoughby and Miss Grey); shallow interests (Anne and Sir Middleton and, again gently, Mrs. Jennings); the power of external beauty, which passes from importance (Charlotte Palmer); and shallow, irrational opinions based on unreasoning sensibility (again, Marianne and Willoughby along with Robert and Mrs. Ferrars and John and Fanny Dashwood).