Deliberate mistake: In the scene where The Pussycats' first single, "Pretend to Be Nice," is being progressed up the Billboard chart, as the camera is scrolling down the list of singles the song "Missing Sneakers" is actually listed in two different chart positions for that same week. Everyone knows that the same exact song can't be listed twice in one week on the same chart.
Continuity mistake: In the scene where Josie is fixing Alan M's truck, she puts her hand on the side of the truck and knocks over the wrench. You can clearly see that she knocks over the wrench and what looks like a roll of tape. But in the next shot you can see that the wrench was the only thing that fell.
Continuity mistake: In the scene where Wyatt first meets the Pussycats on the street, he holds up a clear CD case to highlight the girls in it. Before he holds it up, it has a CD in it, which he tosses to the side. The case itself also has the grooves for the disc and the CD logo imprint in the corner. When Wyatt holds up the disc cover, its completely clear and devoid of any grooves for the CD to go into or the upraised CD logo.
Revealing mistake: When Josie is playing "Pretend To Be Nice" in the studio, she plays the first two chords backwards. It looks like it should be right, but any guitar player would notice it.
Continuity mistake: When Mel and Val are at the supposed TRL, Mel picks up the fake sign and drops it on the floor. When Carson runs after her she drops the sign again and a minute later the other guy knocks over the sign once more with his baseball bat.
Continuity mistake: At the end when Josie and Fiona are fighting, Josie stuffs a Twinkie in Fiona's mouth. When the camera changes angles, all traces of the Twinkie are gone from Fiona's face. When the camera switches again, right before Fiona smashes the guitar, there is a little bit of Twinkie on Fiona's face.
Continuity mistake: At Fiona's party, after Fiona performs, from the front there is a shot of Josie and she is clapping and her arms are up; then there is a shot from behind and her arms are down.
Continuity mistake: The Pussycats' single enters the charts at No.80 odd and works its way up to No.1. This would take a few weeks as charts are calculated on a weekly basis. However, Josie remarks after they have a No.1 single that it is strange that it all happened in a week. That would not be possible.
Continuity mistake: During the scene where Melody and Valerie go on "TRL", and Carson Daly tries to kill Melody, they are on the bleachers with all of the cardboard cutouts of famous celebrities. About halfway through this scene, Carson swings the bat and misses Melody, but it breaks the Christina Aguilera cardboard cutout. However, later on after he broke it, you see the Christina Aguilera cutout standing up in one piece, when it was broken and had fallen off of the bleachers before. [Actually in this scene if you pay attention there are multiple copies of the cardboard cut outs of everyone. There are at least two copies of Matt Damon & Christina Aguilera.]