When Charlie shows Peggy Sue the book that Michael Fitzsimmons dedicated to her, it switches from having a dust jacket to not having one, and then back again.
Maddie's hair style changes between shots when Peggy first sees her outside at the reunion, when they are inside and Maddie tells Peggy to find a table, and when Maddie and her husband join the table.
When Carol and Maddie are driving Peggy Sue home after giving blood, on the way to Peggy's house, they pass the same blue car and the same red car three different times.
When Peggy faints at the reunion, Charlie is on her left side. In the next shot, Charlie is in the background, and Beth looks back at him. In the next shot, he is back at her left side.
When Peggy Sue and Charlie speak during her majorette practices, it appears to be sunset. This scene is before her date with Richard at 4:30 p.m. in which the daylight it's much clearer.
The huge moose head over the bookshelf in Mr. Kelcher's den would have been impossible to get through the front door at any angle.
The foil balloon is NOT an anachronism. It is a remnant from the 1986 reunion that Peggy Sue notices, to further confuse her/the viewer as to whether she has time traveled or is dreaming. It's intentionally there, it's not an anachronism.
In the opening mirror shot's TV image, the text is legible, but TV image should have appeared reversed if being viewed in a mirror.
At beginning of movie, Peggy Sue and the actions of her reflection in the mirror don't match up exactly. Most of the mirror scenes were done with doubles in reverse, making synchronized movements very hard.
Peggy's dad brings home a "new" Edsel, which is a 1958 model, in the April 1960 setting of the movie. There was a 1960 Edsel, but its production was phased out by Ford Motor Company in November 1959 after only 2,846 of the 1960 model were built.
The Bose speakers at the "teen make-out dance party" didn't exist in 1960. Bose Corporation was founded in 1964. The distinctively shaped Bose 901 "Direct/Reflecting" speakers on shelves on the wall (above Charlie and his singing group) first appeared in 1968.
During the scene where Peggy goes into the record store, the road can be seen through the window. The road has double yellow road striping. MUCDT did not introduce / roll out double yellow striping until 1961 and even then would not have been popular until at least 1963/4. Double white stripes, or single white or yellow would have been valid at the time.
When Richard Norvick tells Peggy Sue to stand in front of a responding fire engine to see if she is dead, the fire truck is the correct style for the era, but the helmets that the firefighters are wearing are of modern fiberglass design with a salad bowl shape that didn't come into vogue until the 1980s when the movie was made. Fire helmets of the 1960s would have been of tin or leather construction with a more traditional shape.
About 40 minutes into the picture Peggy Sue is having a conversation with science genius Richard Norvick. At the board at the front of the classroom, in the background behind the characters, there's a characterization of Saturn, with a couple of its moons; this characterization would have been impossible back in 1960, when supposedly the scene is taking place. The details are way too vivid and could only have become possible in the mid-1980's, which is exactly when the film was being shot.
When Peggy Sue tells Richard that she had "come from the future," you can see that she actually said "back from the future" by watching her lips. The line was apparently overdubbed later so the movie wouldn't make viewers think of the recently-released hit movie Back to the Future (1985).
When Carol and Maddie are in Peggy's room asking about her date with Michael Fitzsimmons, the camera angle shows all three girls. Maddie says "Yeah, he's so cool and mysterious," but her mouth doesn't move.
When Peggy Sue is pulling board games out with her sister, she says "chutes and ladders" but appears to be mouthing an alternative name for the game, "snakes and ladders".
When Peggy Sue wakes up in 1960, she is wearing the same dress from the reunion which has changed from silver lamé to pale blue taffeta. The dress is full-skirted with a revealing bodice yet no one questions why she is wearing a formal dress to school.
When Peggy Sue asks the lingerie lady if they have pantyhose in stock, she acts as if she'd never heard of it. In 1960, pantyhose was not worn by women every day but it was well known in the dancing industry. The sales woman would have known what it was and just told her they don't carry dancers supplies.
Michael says that polygamy is legal in Utah. This is an urban legend; polygamy was outlawed in the U.S. in 1882 and by the Utah territory in 1890 (because Utah was being denied statehood because of it).
In the past Peggy Sue tells her sister not to eat the red M&Ms as they're bad for her. This was an inaccurate but common belief among consumers in the 1980s, Peggy Sue's present and when the film was made, because the food additive Red Dye No. 2 was found to cause tumors in rats. M&Ms never used Red No. 2 and weren't bad for you, but they removed the red M&Ms from production anyway to avoid scaring consumers who'd heard about the bad red dye from the news. They quietly reintroduced red M&Ms about a decade later.
Charlie accidentally juxtaposes his words when he says "The Tigers have got four 20-game potential winners." He means to say "The Tigers have got four potential 20-game winners."
Peggy Sue reacts to her dad buying an Edsel with laughter and great surprise. Since she remembers the events of her youth, this wouldn't have been a surprise.