This is funny just as it is absurd to think that there is an “outdated side” of a street. The absurdity continues as Wilde implies that Lady Bracknell thinks this could be "easily changed", showing that she expects Jack to change the side of the street he lives on if he wishes to marry his daughter. This is a completely ridiculous and unbelievable request. The fact that Jack wonders whether Lady Bracknell meant "the fashion or the side?" he creates the play simply because he questions it as it implies that both of these factors could affect the quality of life led by the upper class. Wilde shows that just the thought that the upper classes are so ostentatious and can believe it, provokes laughter.