Continuity mistake: During the first scene set in a prison cell, as Martin Luxford (played by Hugo Speer) is about to be released, there is a glitter ball made from an orange covered in tin foil. It is rotating first one way and then the other, as it has been spun by hand. As the film action cuts between the two characters, the ball mysteriously changes direction without having slowed down and at one point appears stopped, having previously been rotating rather fast.
Factual error: In the scene where Mystery is playing "Rock & Roll All Nite" in the basement, Hawk is playing an Epiphone Special II guitar. The movie is set in 1978, and this guitar did not hit the market until 1996.
Continuity mistake: At the Unicorn Bar Evie takes a photo of "Drumstrings" Casey performing as Faye-Jean dances in front of him. Both Drumstrings and Faye-Jean are facing Evie with Faye-Jean holding a beer bottle over her head in her left arm. Later when Evie looks at the photo, it has been taken from the side and Faye-Jean is facing a different direction, no arms above her head and is not holding a beer.
Continuity mistake: When Roberta is in Brian's apartment, she is putting curlers in her hair and then Brian walks in and they start talking. Roberta then stands up and Brian kisses her neck and as she turns around you can see the curlers have disappeared.
Factual error: One of the operetta excerpts shown in the movie is the humorous song "This Helmet I Suppose," during which Princess Ida's three brothers are supposed to remove their armor piece by piece, finding it heavy, hot and awkward. Partly as a result of this, the three are soon afterwards quickly and easily defeated in combat. In the film, however, only Arac, the brother singing the verses (played by Richard Temple (played by Timothy Spall)), removes his armor. The others simply stand still. (This might have made the battle scene end differently if it was shown on screen!)
Visible crew/equipment: In the scene where Sean Penn is playing with the big band fronted by the female singer, there is a microphone on a boom visible top center of the frame, when the camera does a pullback to show the whole band at the song's end. (VHS version.)
Factual error: While Nate and his business associates are driving around in downtown Baltimore, the Key Bridge (which spans Baltimore harbor) is visible in the background. The movie was set in 1954; the Key Bridge was built in 1972, 18 years later. (01:33:55)
Continuity mistake: In "Rhapsody in Blue" When we first see the drumming construction worker in his room, his alarm clock is standing up straight, but when the closeup happens, the clock is face flat on the table. (00:17:45)