This paper will look at the character of “the Doctor” in three medieval performance pieces: The Play of St. George, a Christmas mumming, The Croxton Play of the Sacrament, and Christopher Marlowe’s Doctor Faustus. These three works provide an excellent counterpoint to the Doctor character that appears in morality plays from the same era (as in, for instance, Everyman): in these three plays, the Doctor appears as a figure of fun, a source for comedy, very different figure from his purely allegorical, doctrinally-correct presence in the moralities. Interestingly, determining the date of composition or first performance for all three of these Doctor plays is problematic, if not impossible. While this makes any analytical approach rooted in a strictly evolutionary timeline impossible, it does open the works up for discussion of their relationship through genealogical terms (as originated by Michel Foucault and adapted by Joseph Roach into the idea of performance genealogies). Using a close reading of the first two texts particularly, I examine them for signs of genealogical relationship and examine the particular representational strategies they employ. I suggest that they form a distinct genealogy that informs Marlowe’s play in a much more immediate and significant manner than morality plays that are traditionally seen as a commanding influence on Faustus.