Deliberate mistake: Joseph (John) Merrick's speech was never as audible as shown in the film, and several operations were needed before he could speak at all. Even after that, Frederick Treves often had to "translate" what Merrick said because the majority of people still had problems understanding him. [Probably changed to simplify the storytelling, but still inaccurate].
The Elephant Man (1980)
Ending / spoiler
Directed by: David Lynch
Starring: Anthony Hopkins, John Hurt, Anne Bancroft, John Gielgud
Merrick's former owner breaks into the hospital, and kidnaps him, taking him back to the circus. The other freaks help Merrick to escape, and he makes it back to King's Cross station in London, where a bunch of kids unmask him. A crowd attacks him, intending to lynch him, but John retorts with his famous "I am not an animal - I am a human being" speech. He is returned to the hospital by the police, and taken to the theatre by the Princess of Wales, where the actress he met earlier dedicates the show to him. That night, Merrick decides to go to sleep in a "normal" position, even though he knows it will cause him to suffocate.
Dave
More mistakes in The Elephant Man
John Merrick: No! I am not an animal! I am a human being! I. Am... A man!
Trivia: Director David Lynch has a cameo as a member of the angry mob who chases John Merrick when he returns to London.