Revealing Mistake: When the TARDIS takes off, the lab set blurs distinctly, with doubling of many small items in the lab such as the chair and the probes. This is because the camera was moved during the "roll back and mix" used to make the TARDIS disappear.
Revealing Mistake: As Tommy enters the room where the Doctor, Sarah and Mike Yates are talking with Cho-je, the camera follows him in but then bumps into something with an audible "clunk" and a shaking of the image.
The Doctor: There's only one thing for me to do, Mike. I've got to go after her to Metebelis III.
Mike: In the TARDIS?
The Doctor: Yes, of course.
Mike: But how can you be sure you'll get there?
The Doctor: The TARDIS may be a little erratic, I'll admit. But Metebelis III is the one planet I'm absolutely certain of reaching. I wired the coordinates into the programmer.
Mike: But Doctor, a planet's a big place.
The Doctor: Yes, well, I always leave the actual landing to the TARDIS herself. She's no fool you know.
Mike: You speak as if she were alive.
Doctor [ smiling ]: Yes. Yes I do, don't I?
Kismet Delgado, who provides spider voices, is the widow of Roger Delgado, who played the Master in Seasons 8 to 10.