Joseph Lister

Joseph Lister was a physician and academic from Glasgow under whose tutelage the First Doctor took a medical degree. The newly-regenerated Second Doctor told Polly that he got the degree in 1888. (TV: The Moonbase) Later incarnations created confusion about their relationship to Lister. The Fourth Doctor mentioned Lister on his CV, but claimed the degree dated to 1880. (PROSE: System Shock) Meanwhile, the Fifth Doctor told Peri that he was more than qualified to offer medical services in the American Civil War, because he'd gotten a degree from Glasgow. (PROSE: Blood and Hope)

Behind the scenes
Technically, no DWU source provides Lister's first name, but the gag doesn't work unless "Lister" is meant to be taken as "Joseph Lister".