William Hartnell described the Doctor as "a wizard", and "a cross between the Wizard of Oz and Father Christmas". Paul McGann, who played a later incarnation of the Doctor, said Hartnell's "seemed like a Victorian, someone kind of stern and paterfamilias about him. Something kind but scary". One quirk of the First Doctor was his tendency to become occasionally tongue-tied and stumble over words. Sometimes this was a deliberate acting choice: William Russell recalls that it was Hartnell's idea for the Doctor to get Ian Chesterton's surname wrong, calling him "Chesserman", "Chatterton" and even "Charterhouse". This character choice also gave the series' producers the ability to use takes in which Hartnell flubbed his lines. Due to the series' tight production schedule, it was rarely possible to reshoot such scenes and dubbing the dialogue was usually not an option. Hartnell suffered from undiagnosed arteriosclerosis, which affected his ability to remember lines, increasingly so as his time on the series progressed.