During a crane shot of the Rock and Roll Hall of Fame show Fish's drum set appears as a larger drum set with two bass drums instead of the smaller setup with just one bass drum with "A.D.D." written on it.
During the Rock and Roll Hall of Fame show, when A.D.D. come back onto the stage to play, there is a scene where Amelia is singing into the Mic, but as the scene changes she appears at the back of the stage next to "Fish". As the scene changes again she is next to her Mic again.
When ADD goes up the stairs to the stage for the encore after Vesuvius leaves Matt has no hat on, and is not holding one. However, he is wearing a dark blue hat in the music scene following. He threw his gray hat to a fan earlier.
During the opening song of ADD opening for Vesuvius, the crane shot from a distance shows not only the two bass drum kit of Vesuvius, but Curtis and Amelia playing their guitars left handed, instead of right handed, like they have throughout the movie.
Just before Jeremy enters to tell the group he cant play the prom, Amelia flips off Curtis and drops her arm. In the next shot after Jeremy enters, she is still half flipping him off and her arm sort of just hangs there.
During the first dinner scene, Fish says the last time he saw Matt that he was building a robot. Matt responds that it was when he was 10. Later when Matt is asking fish to drum for them he says that Fish called him Max until he was 11.
When Fish is dumped by his girlfriend at the beginning, he walks to his sister's house to crash, and he is shown walking North past the Rock & Roll Hall of Fame to get there. Not only is there no residential area in that direction, but if he walked just a little bit further, he would walk right into Lake Erie, as the Rock Hall is on the Erie shore.
When the Taxi carrying Fish pulls up in front of Mr. Lee's Restaurant, a 416 Area Code (Toronto) is visible on a sign, as well as the word Toronto on another sign. This row of businesses is in Chinatown, on Spadina Ave.
Vesuvius is slated to be inducted into the Rock and Roll Hall of Fame after 20 years together. However, artists aren't eligible for induction (barring an extenuating circumstance) until 25 years have passed since the artist released his/her/their debut.
When the video director asks the band to read the words backwards, he has a sign held up for them to read backwards words. However, the word 'mistake' is spelled as k-a-t-e-s-i-m when it should be e-k-a-t-s-i-m. If you sound out "k-a-t-e-s-i-m" phonetically, it would be "mistake" backwards. "e-k-a-t-s-i-m" wouldn't work.
Matt comes to Lee's basement to present Fish with a laptop and web-cam to practice, but Matt wouldn't know where Fish was staying as Matt was grounded so could not use the phone, Fish is not seen to own a phone and Matt's mum would not want to stay in contact with Fish.
When Amelia and Matt are playing Rock Band on the tour bus, the notes continue to be hit on the TV after they stop playing the Rock Band guitars to talk, and it switches from one player to two between shots.
After Aziz has taken off the plastic wrapping of his new bought Vesuvius CD, he takes it out the box and holds it up with the back facing the camera - The CD is clearly a CD-R with a green recordable back, not a silver backing like any original store bought audio CD would have.
The goof item below may give away important plot points.
When Vesuvius leave the Stage at the end of the movie and A.D.D. reenter it, it can clearly be seen that the drum kit of Vesuvius is covered again and the much smaller drum kit of Fish is on Stage, which wasn't their when Vesuvius started to "play".