When Galleria is playing the piano by herself at school, it's obvious she really isn't playing. Her hands are moving way too slow for some of the parts and at the end, her hands are playing very low on the bass notes when the notes heard are in middle-low C range.
At the beginning when they are singing, Dorinda, Chanel and Aqua fall over, but Galleria is still singing when they all get up, one of them puts her hand on Galleria's shoulder, you can hear her voice but her mouth is not moving
When the girls are performing "Cinderella" in the beginning of the song when they look upward towards the camera, you can clearly see Galleria mouthing "look up look up" to Chanel and then you see Chanel's head look up.
When Galleria's talking on the phone with Chanel, and her dad comes in for the second time, she presses the hold button on the phone, and when she gets back on the phone, she doesn't press anything but just starts talking.
When the girls are sitting at the lunch table and Galleria finishes talking to Jackal's office on her cell phone, she lays the phone down on her tray with the flip part still open. The phone stays open the entire scene, but when Derrick and Mackerel leave to go to the newspaper office, the flip phone is closed.
The goof item below may give away important plot points.
Galleria's dog gets stuck in a pot hole at the end of the movie. In result, the entire town shuts down, and almost all the firemen rush in to help get the dog out. This is completely unrealistic and it would not take half of the fire department to get a dog out of a hole, nor would it cause so much commotion.