Revealing mistake: During the prom scene, especially during the song "(Don't You) Forget About Me", none of the band guys (especially the older man keyboard player) are actually playing their instruments.
Revealing mistake: When Jim is stripping, if you look at the computer screens you can see a line of text to the right of the video that reads "Duration 0:00:19:26." However, the stream is "live" so the duration should not be static. (00:48:20)
Revealing mistake: During the choir duet with Oz, most of the audience is cardboard cutouts. This is very obvious.
Revealing mistake: When Kevin is sitting outside the prom alone throwing pennies into a cup, there's the sound of them hitting the bottom, but if you look closely you can see nothing goes into the cup. (01:11:30)
Answer: The song is called Sway by Bic Runga.