Christopher Lee on his time filming The Curse of Frankenstein (1957): ''I was never so content.''
Lee credited the film with helping him adjust to the horror genre.

Sometimes you can’t understand someone else’s plight without walking a mile in their shoes. In Christopher Lee’s case, he had to step into the shoes of The Creature to truly understand those who had previously taken up the monster’s mantle.
Lee played the Creature in the 1957 film, The Curse of Frankenstein. Accepting the role wasn’t an issue; Lee had played his fair share of menacing characters. But acting in this film gave him a much deeper appreciation for the actor who had previously played the role of the Monster, Boris Karloff.
“Playing the Creature taught me to appreciate just how great the skill was that Boris had used in creating his Monster,” wrote Lee in his autobiography, Lord of Misrule. “And perhaps, in a way, that helped me to adjust to the very notion of working in the horror genre. It was a case of inventing a being who was neither oneself nor anybody else, but a composite of pieces of other people, mostly dead.”
Lee went on to admit that while working on The Curse of Frankenstein was difficult, it fulfilled him in a way that he had never expected.
“It was absorbing work,” wrote the actor. “I was never so content. The five weeks of the schedule flowed by, plus a sixth because the sensation had grown at Hammer that we were on to something and the ship mustn’t be spoilt for a ha’p’orth of tar."