Deliberate mistake: When Joey and Jonathan get in Joey's car at Metropolis (just before heading to the police station), the car has headrests. When they get to the police station, see Lance Gessler leaving and then follow him, the car no longer has headrests. Obviously removed so as not to obstruct the actors.
Jonathan Creek (1997)
1 deliberate mistake in The Grinning Man
Starring: Alan Davies, Caroline Quentin, Stuart Milligan
The Sinner and the Sandman - S5-E2
Factual error: Members of The Salvation Army do not gamble and do not buy lottery tickets.
Madeline Magellan: Enough with the pedanticism and let us eat.
Jonathan Creek: The word is pedantry.
Question: What exactly did Jonathan and Maddie give to the tramp in exchange for information?
Answer: It was actually mouthwash.
Chosen answer: It was a bottle of turpentine.
Methylated spirit, always coloured purple.