Factual error: When the boys start their hike at the railroad yard, there is a modern transformer on a pole in the background. In 1959, they were smaller and black. (00:15:00)
Factual error: There are aluminium cans in the general store. The first all-aluminium cans of this style weren't used in 1959, when the film is set. (00:24:05)
Factual error: When Gordy goes to get supplies at the store, as he is standing there the clerk is talking about Denny, and in the background on the shelf there is a bottle of Soft Scrub. It's supposed to be the 1960s, but Soft Scrub was not around until the early 80s. (00:25:00)
Factual error: When they find the dead body, the body looks like it has been dead for only a short while, his face even had a pinkish color to it still. Factually, the body would be a lot more decomposed after a few days, bluish or white in color from the blood pooling at the bottom of the body, since the body was on its back. (01:08:30)
Factual error: After Wil Wheaton fires a warning shot, he points the pistol at Kiefer Sutherland and pulls the hammer back to threaten him. However, this is a semi-automatic pistol, and the hammer would already be cocked after the shot he fired. (01:13:40)
Factual error: Teddy wears army boots that did not exist in 1959.
Factual error: When the two drivers of the teenage gang are playing "Chicken" on a straight section of a two-lane highway, the center lines of the road consist of yellow hashmarks. Though the picture was set in 1959, center lines for passing zones on two-lane highways were painted white until 1971.
Factual error: Near the end of the movie, when the boys return to town, a garage door in the background is a modern metal roll-up type that was not available in 1959.
Factual error: When Ace and friends are racing/playing chicken, the license plates on both vehicles are from California and the wrong colours from 1959. They should be black letters on a yellow background. However, one has yellow letters on a black background, which wasn't available until 1962. The other car, also with a California plate, has a blue background with yellow letters, which wasn't available until 1969.
Factual error: The gold 50s Cadillac in the junkyard has a red wall tire on the rear which was not available until the mid 60s.
Factual error: There's a scene with a house in the background that has the electric wires from the power pole going to a connection above the roof. In 1959, the connection would have been made under the eaves or on the outer wall.
Answer: A cello.