Credit Error: "Yates' Guard" is listed in the credits as "Yate's Guard".
Revealing Mistakes: When Jones is looking through his microscope, the objective is rotated so that none of the lenses actually point at the slide.
Professor Jones:: (in irritation, when Jo tries to clean up the mess she just made) Leave it! I shudder to think what might happen.
Stevens: (after telling the Doctor not to return) You would be received with considerably less courtesy.
Jo: You know, when I first started working for UNIT, the Brigadier told me this was going to be my job. You know, holding test tubes for the Doctor, and telling him how brilliant he was. Never seemed to get around to it though, somehow.
Professor Jones: Pretty dull sort of job.
Jo: I don't know, I'm rather enjoying this.
Professor Jones: Aye, so am I.
(The Doctor has disguised himself as a cleaning woman.)
The Doctor: You say one word!
Mike Yates ( after a long amused pause): I like your handbag.
The Doctor: Do you? Well watch out I don't slosh you with it!