Continuity mistake: Nevel gets some tapenade on his face, but the amount isn't consistent. When he looks at Spencer you can see there is more on his face.
Continuity mistake: Spencer arrives at his destination with butter on his elbow but it disappears a few moments later.
Answer: In direction translation it means 'Mischievous Spirit'. 'Hob' as in HobGoblin means clown or prankster, and 'Knocker' was an old age term for Poltergeists in mines. Miners would often complain of hearing knocking sounds down mines when there was no-one else down there, hence 'Knocker'. It's not a regular English expression though.
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