Starring: Alexander Armstrong, Daniel Anthony, Elisabeth Sladen, Tommy Knight
Goodbye, Sarah Jane Smith: Part 2 - S4-E12
Revealing mistake: In the shot in Sarah Jane's attic right after Ruby is thrown into the sun, the group are talking in the attic and to the left of the screen, you can see that the blue screen used to create Mr Smith is visible.
Mona Lisa's Revenge (1) - S3-E10
Other mistake: Mr. Smith scans the Mona Lisa and determines that it is genuine from DaVinci's brush strokes. He should have also noticed the words "This is a fake" written in felt tip under the paint, from when The Doctor replaced the Mona Lisa with one of DaVinci's "forgeries" in "City of Death."