The Trial of a Time Lord 13-14 (aka The Ultimate Foe) - S23-E4
Factual error: The Master states that Earth and its entire constellation were moved, but constellations are merely patterns of stars (as viewed from a given point, like Earth) that may be nowhere near each other - the Earth could not really be described as being in a constellation as any sort of specific entity that could be moved.
Revealing mistake: (Ep. 4) After Omega takes off his mask and looks in the mirror, when he sees that his physical body doesn't exist he puts his mask back on and screams, but when he shouts, "If I exist only by my will, then my will is to destroy," Omega's mask pops up off his face, and we can see the actor's blackened face as he shouts the last bit of his dialogue. (00:07:10)
The Doctor: This is a situation that requires tact and finesse. Fortunately, I am blessed with both.
Planet of the Spiders - S11-E5
Trivia: The first thing the Third Doctor does on-screen is collapse out of the TARDIS, which is also the last thing he does in that incarnation.
Question: I wanted to know what was the name of the episode where these cancerous creatures suck the bones out of you and turn you into a pile of mush - it was one of the first episodes I think.
Answer: I don't think this was a Doctor Who story. It sounds more like the 1966 film "Island of Terror" (although it did star Peter Cushing who played Dr Who in two Dalek movies around the same time).
Answer: Your right it is, "Island of Terror."