Factual error: The teacher in shop class is reading a newspaper with a headline about the Jim Jones suicide cult in Guyana, saying bodies were found, etc. However, the cult did not take the cyanide Kool-Aid until November 18, 1978, the concert in Detroit takes place October 13, over a month before the Jim Jones suicide/massacre.
Factual error: In the convenience store scene, the kid in the Ace makeup is playing a KISS pinball machine. The movie is set in 1978, so this is impossible, as the KISS pinball machine didn't hit the streets until summer 1979.
Factual error: In the beginning when Mystery is practising there's a close-up of Jam's bass drum and judging by the indentations and shape the basshead is on very loose. That would mean the strokes would be very sloppy and resonant, but the beats we hear are sharp and hard.
Factual error: The Pizza Pig delivery driver arrives to the parochial school in a pink Lada Niva. Russian Ladas have never been imported into the States, and though it may be argued it have been purchased and brought into the US from Canada, since Canada did import them for awhile, the Lada is a late 80's model, and the movie takes place in 1978.