Trivia: Because "Candy Man" is a slang term for a drug dealer, the song has been banned in many schools.
Trivia: The tinker that startles Charlie outside the gates of the factory quotes from the poem "The Fairies" by William Allingham. "Up the airy mountain, Down the rushing glen."
Trivia: The 'Golden Goose Egg' scene was shot on Julie Dawn Cole's (Veruca) 13th birthday.
Trivia: The foam sprouting from the machine Wonka takes through the Wonkawash was actually the foam from a number of fire extinguishers.
Trivia: Allegedly Roald Dahl once tuned into a TV airing of this film while staying at a hotel. Due to having sworn never to see the movie it took a good 15 minutes before he realized what he was watching and immediately changed the channel in disgust.
Trivia: None of the kids were allowed to see the chocolate factory set beforehand, so that their looks of surprise upon seeing it were genuine. But Julie Dawn Cole, who played Veruca, recently admitted that when she was on the set a few weeks earlier to record her song, a stagehand let her take a look at it.
Trivia: The daffodil that Gene Wilder eats at the end of the pure imagination song was not made of rice paper or anything nice it was made out of wax, that he had to chew and then spit out when the camera stopped rolling.
Trivia: Denise Nickerson received thirteen cavities in her teeth because of all the gum she had to chew on set as Violet. (According to her, there was no sugarless gum back when the movie was filmed).
Trivia: When Mr. Turkentine asks for Charlie's help with an experiment, he states that two of the main ingredients he would be using are Nitric Acid and Gylcerine. He then goes on to mention that when poured in equal amounts they would create a very powerful wart remover. Nitric Acid and Gylcerine when mixed together actually creates Nitroglycerine, a very powerful liquid explosive - "powerful wart remover" is a bit of an understatement.
Answer: Closed circuit security was invented in 1942 and came into common use in the late 60s and early 70s. Beyond that, Wonka could have had Oompa Loompas monitoring the group or simply noticed that they were gone and guessed.
Greg Dwyer