Continuity mistake: When JB dreams about singing "Master Exploder" in the small bar, he points at one guy in the audience and literally blows his mind. When he starts pointing you can not only see JB's face, but also how his elbow is in a slight angle. In the next shot the camera shows the guy JB is pointing at and his elbow is completely stretched. The views change several times and the angle of his elbow changes after every cut, until the guy's brain is finally blown out.
Continuity mistake: When JB is in Hollywood for the first time and the guy plays Bach, you can see two Goths walk past and in the next shot the same guys walk past again.
Continuity mistake: When JB and KG are powersliding under the gate in the Rock n' Roll history museum, in one of the shots the gate is so far down that they would not be able to slide under. In the next shot the gate has moved up. (01:07:00 - 01:12:00)