Shakespeare portrays Don John as a scoundrel meant to cause mischief and harm from the onset of the play. The Dramatis Personae classifies Don John as "Don Pedro's bastard brother," letting the audience know from the very beginning that Don John is not an equal to his brother, at least in terms of breeding. In Act One, scene three, Don John reveals his contempt for his half-brother's status and the fact that he always must play the role of sycophant to Don Pedro, stating that he "rather be a canker in a hedge than a rose in his grace" (I.iii.21-22). Moreover, Don John makes his malevolent feelings clear when he states:
In this, though I cannot be said to be a flattering honest man, it must not be denied but I am a plain-dealing villain (I.iii.23-24)
Shakespeare clearly depicts Don John as the play's villain, characterizing him as a man who has bitter feelings toward his brother and Claudio. By the end of Act One, Don John reveals both his malcontent and his plans to uncover "any model to build mischief on" (I.iii. 37) as he learns of Claudio's plans to woo Hero.