When Patricia is explaining to her husband about her "roommate" in the car, she is holding papers. There is a office clip holding the paper together. The metal flaps on the clip switch between being up and being down.
At the record store, one of the walls has a spread of Iron Maiden's 1986 album "Somewhere in Time" on it. The artwork featured is the artwork from the 1998 CD remaster; the artwork that the album had until then had the band's name and album title displayed much smaller and to the top left corner.
The first time Sherrie and Drew go into the Tower Records store to browse, Skid Row's "I Remember You" can be heard over the store speakers. The time frame for the movie is 1987 and "I Remember You" was not released until 1989.
The angle of Stacee's head changes during his interview by Rolling Stone magazine. At the beginning of the interview, he sits up and leans forward on the couch, and starts to say, "I think, due to the changing nature of the music industry..." with his head leaning to his left. The camera angle changes, and his head is instantly leaning to his right.
The story is set in 1987 but the characters sing songs written after that year, including Warrant's 'Heaven' (1988), Extreme's 'More Than Words' (1990), Poison's 'Every Rose Has Its Thorn' (1988), and Skid Row's 'I Remember You' (1989). Within the movie's "musical" illusion of reality, these songs are meant to be representative of the mid-1980s-through-early-1990s era as a whole, since this film is a nostalgic fantasy representation of the era rather than a historically accurate recreation of a specific year. Keep in mind also that an important plot element is the notion that the song "Don't Stop Believin'" is written in 1987 by the fictitious Drew Boley, but in real life was written by Journey in 1981, and was already a well known song by 1987.
During Drew's first performance on stage in front of the crowd, Drew keeps switching the way he is holding the guitar. This is due to the mirror effect that is shown by the fact that the writing on his shirt also changes.
During the interview scene while they are singing "I Want to Know What Love Is", Stacie's chest tattoo changes sides from left, to right and then back to left. However, this is explained by being in front of a mirror.