Anton Diffring was the second choice for the role of Georges Bonnet, after Peter Cushing turned it down shortly before filming began. When Cushing claimed illness after breaking his oral commitment, the studio threatened legal action against its biggest star but didn't follow through.
Dr. Georges Bonner: [Before unveiling the bust]
I would like to say at this stage that any credit due for what you are about to see should be laid at the feet of my charming young model. An artist cannot form a thing of beauty unless he has a thing of beauty from which to draw inspiration.