Deliberate mistake: The morning after the flyers are spread, Buster is sleeping in a drawer. When his alarm clock goes off, he hits his head at the top of the drawer, but later on, he can be seen standing up in it, easily visible when he is putting his coat on. The drawer obviously became wider for him to stand up in it.
Plot hole: After Moon gives his first pep talk about working harder than ever to the contestants, Eddie asks loudly "What about the hundred grand?!" in earshot of most of the contestants. The contestants (especially Johnny or Pete) would have heard that question and started asking their own. (00:24:50)
Other mistake: When Mike finishes his song and the audience begins applauding him, you can see the microphone cord dangling from somewhere above the sets, despite it previously having its stand on the stage. This is obvious when he's swinging from it. What is it hanging from, thin air? There was nothing he could attach it to while swinging; the cord should've snapped rather than holding.
Factual error: The police are circling the theatre to find out where Johnny's escaped father is. During this, you can see that Mike is getting pulled upwards towards the copters like a piece of metal getting attracted to a magnet. Helicopters create downdrafts - Mike should've been blown away from the stage rather than being pulled up.
Answer: It would have to do with paying royalties to the artists if the songs were included on the soundtrack album. The artists would be paid a one-time flat fee for their songs to be used in the movies or the trailers, but for albums being sold would mean some of the profits would have go to the artists. The movie studio can make just as much on the soundtrack album without certain songs being included. Regarding the title, it may be the artist wanted it changed for some reason, or the filmmakers felt it didn't fit in.
raywest ★