Viola was a character in William Shakespeare's play Twelfth Night.
While outlining the play in a meeting with Richard Burbage and the Fifth Doctor, Shakespeare described Viola's role in the plot. He said he had a mind to write of "a woman who was shipwrecked" who, "fearing her brother [was] lost at sea and anxious for her own safety, doth counterfeit her own brother in character and apparel". He went on to say that Viola, therefore dressed as a man, would be "employed to carry favours of love between two estranged lovers". In doing so, "she herself doth fall in love with the man" while "the woman doth fall in love with Viola, thinking her to be a man also".
The Doctor determined this plot to be "rather complicated" and not "make much sense", questioning who would mistake a woman dressed as a man for the real thing. Burbage elaborated that she would be played by a boy. He still wasn't convinced and suggested what would happen if Viola's brother turned up, asking if it would be confusing for both the characters and the audience "if someone [met] the brother and [thought] it's the boy being a girl who's pretending to be the brother but [was] actually the sister". Burbage exclaimed that this hypothetical scenario had to be included. The Doctor later criticised Shakespeare's choice of title, stating that he didn't see "what Twelfth Night ha[d] to do with a love triangle between a man, a woman, and a cross-dressing woman played by a boy". (PROSE: Diary Extract)