Both Mad World and Trick use meta-theatrical speech to indicate "tricking" or "playing a part" on stage. The more formal and mannered a character’s speech is, the more that character is acting a part within the play, either for other characters on stage or, in soliloquy, for the self.
In both, actors play characters playing characters, sometimes down to three or four levels of performativity, depending on the gender of the actor/character. Characters often slip between blank verse and prose, sprinkled with rhyming couplets here and there. Prose is used when someone is describing something mundane, or letting lose with strong, un-edited thoughts and feelings. Blank verse seems to be reserved for speech that has received the internal editor, thoughts that are intended to persuade someone.
Rhyming verse, specifically, seems to signal a character’s shift into a trictster persona who ostensibly follows normative social and sexual mores, but whose speech may be intended to gull the audience. Often rhyming couplets are sententious aphorisms that express the cultural norms rather than a character’s deeply held beliefs. At the end of Trick, both Jane and Follywit engage in long rhyming speeches promising new faithfulness and righteous actions; to different degrees, however, their previous actions do not support such a change. Are they playing “the wife” or “the husband” for now, intending to engage in more tricks later?
Sometimes even the rhythm of rhyming speech, such as the Courtesan’s catechizing of the Wife in Mad World, can signal this shift. The words the Courtesan uses undermine accepted sexual morality while upholding expected sexual roles (the adulterous wife, the jealous husband); her audience on stage, Harebrain, falls for her performance because all he hears is the rhythm of the speech. Her other audience, however, knows that she is performing, for him a role very different than the one she is performing for the Wife.