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 - chronological order
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: Marry me, pretty girl, marry me.
Alice Kinnian: We will marry at... quarter past Wednesday on the 74th of November, and our anniversary will happily be... on those days where we both remember.
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.).