Continuity mistake: In the scene where Drew and his band are setting up on stage, just about to do "Heaven", you can see the Mic has the decorations on it. Then just before Lonny goes to put them on they magically disappear.
Factual error: In the Bourbon they use moving lights which were first used in 1980 actually the ones used were first produced in 1998.
Factual error: When Sherrie and Drew are in Tower Records, the background song is I Remember You by Skid Row. But that album wasn't released until 1989, and the movie is set in 1987.
Factual error: Tom Cruise throws the new Rolling Stone magazine at Paul Giamatti in the latter's office and tells him to look at page 68. Giamatti looks at and starts reading from the right hand page, but in magazines page 1 is the front page, and therefore subsequent pages on the right are odd numbers.
Revealing mistake: In the scene where "More Than Words/Heaven" is sung, there is a montage of shots of Drew playing guitar on stage and Sherrie singing outside. One of the shots of Drew has been horizontally flipped - in it he's now playing guitar left-handed and his "The Bourbon Room" T-shirt has the logo back-to-front.
Factual error: In the scene where Drew and his bands are seeing up on stage you get a clear sight of the drums. The drummer has die cast hoops on his drum set which did not come out till early 90's.
Factual error: There's a poster on Drew's bedroom wall featuring the cover of Not Fakin' It by Michael Monroe, but the album wasn't released until 1989, and the movie is set in 1987.
Continuity mistake: When Catherine Zeta Jones is in the back of the car with her husband, she's holding a sheaf of papers held together with a bulldog clip. First the arms of the clip are up, then they're down, then they're up again.
Factual error: The Hollywood sign is shown as a tourist attraction with platforms, steps, and railings, but in real life none of these features exist and the area is gated and definitely off-limits to the public.