Percy in The Miracle Worker is a young Black servant who, like Martha, works on the Keller estate. He has a small but significant supporting role.
In act 1, he and Martha play with paper dolls as Helen, age six, tries to participate. She tries to understand what the other two are saying by putting her hands to their lips as they speak. When she pokes her fingers into Percy's mouth, he bites them in annoyance, leading the frustrated Helen to put her fingers in her own mouth and bite them herself. When Martha tries to stop her, she tackles her in a rage, threatening her with the scissors the children were using to cut the dolls. Percy rings the bell for help.
In act 2, when Anne Sullivan and Helen are living alone, Percy, who is working at this point as Anne's servant, is used by Anne to try to bait Helen. Anne focuses her attention on Percy, spelling into his hand as Helen tries to get in on the action. Helen, who does not yet understand what the word means, spells "cake" into Percy's hand, so Anne gives her a piece of cake. Anne then shoves Helen aside and spells "milk" into Percy's hand. When Helen wants to know what is going on, Anne spells "milk" into her hand and gives her a glass.
Percy, like Martha, represents the reality that Black people often worked as servants even after the Civil War. Percy's ability to see and speak allows him to articulate what Helen cannot.