The [Flat Earth Society] also took the position that the Apollo Moon landings were a hoax, staged by Hollywood and based on a script by Arthur C. Clarke, a position also held by others not connected to the Flat Earth Society. On hearing this, Clarke sent a facetious letter to NASA's chief administrator:
"Dear Sir, on checking my records, I see that I have never received payment for this work. Could you please look into this matter with some urgency? Otherwise you will be hearing from my solicitors, Messrs Geldsnatch, Geldsnatch and Blubberclutch".
The Wikipedia article on The Flat Earth Society is quite worth reading.