Trivia: Professor Plum reveals that he works for UNO, the United Nations Organization, in a branch called WHO, the World Health Organization. As such, he works for UNOWHO (You Know Who).
Trivia: Not a mistake, just a neat little fact. When the film was being shown at cinemas, only one ending was shown. Different venues had different endings.
Trivia: Professor Plum hypothesizes to the group that the brandy was poisoned. In the original Cluedo board game, poison was included among the possible weapons, and later re-introduced in 1990's game Clue Master Detective.
Trivia: Miss White's "flames on the side of my face" line was ad-libbed by Madeline Kahn.
Answer: Yes, the accent was fake. She wasn't a French maid, she was a prostitute who used to work for Miss Scarlett. She was hired by Mr. Boddy.