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.
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.
In the scene Michael Fitzsimmons and Peggy Sue Kelcher are outside of the Donut Hole cafe, while the song "You Can't Sit Down" by Phil Upchurch was played on the jukebox. This song was originally recorded by the Dovells in 1963.
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.
(Incorrectly regarded as a goof?)About forty minutes into the picture, Peggy Sue is having a conversation with science genius Richard Norvick and if you look carefully 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 utterly impossible back in 1960, when supposedly the scene is taking place. The details seen in this scene are way too vivid, and could only have become possible in the mid-eighties, which is exactly when the film was being shot. The thing is, in this picture, it must be remembered that Peggy Sue is dreaming all this, and could possibly recall what the planet and its moons might actually have looked like, given that it isn't the early sixties in her mind. It really is the middle eighties. Additionally, it's possible that director Coppola has placed the images of Saturn and its moons in the scene as a sort of a little joke on the viewer. You decide.
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.
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 wakes up in 1960, she is wearing the same dress from the reunion which has changed from silver lame' 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.
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.