Continuity mistake: When doctor Nemur, that other doctor, and Mrs. Kinnian are discussing possible complications with Charlie's surgery, there's one shot where Dr. Nemur takes the cigarette out of his mouth and in the next shot it's back in.
Charly (1968)
1 continuity mistake
Directed by: Ralph Nelson
Starring: Cliff Robertson, Claire Bloom, Lilia Skala, Leon Janney
Factual error: There's one scene where Charly's just woken up from his surgery. The next scene shows him working on a puzzle, and he has a full head of hair and no bandages. If he'd just got brain surgery, don't you think he'd still be wearing bandages or at least have his head shaved?
Charly Gordon: That, that is, is. That, that is not, is not. Is that it? It is.
Trivia: This movie is based on the book "Flowers for Algernon." The Simpsons also spoofed this in an episode called "HOMR." (The one where they find that Homer has a crayon up his nose.).