Continuity mistake: In the scene where Viola meets up with Justin at the carnival, in one shot Justin's right collar is flapped down, in the next shot it is up.
Continuity mistake: When Sebastian (really Viola) is trying to impress the guys at Cesario's, she uses her friends as the plan. When her second friend, Yvonne, comes over and starts to walk towards Sebastian (Viola),right before she hugs him, she is really close, but when she actually hugs him she is further back then before.
Continuity mistake: In the carnival fight scene, right after Justin throws a cheap shot at Duke, they fight and fall off the stage. Justin's boxers are black. As they continue fighting, you can see multiple times that Justin's character is now wearing white boxers. The black boxers were his stuntman's. (Confirmed on DVD special features).
Continuity mistake: In the scene where Viola is in the principal's office she retracts her hand twice when he says not to touch the plaque.
Continuity mistake: When Viola reveals that she is a girl she takes her wig of and her real hair is a mess. The camera changes shot to look at Duke but when it goes back to Viola her hair looks normal like it has been brushed.
Continuity mistake: In the scene where Viola is telling her mom she will be staying with her dad for two weeks, her shirt changes. When she's facing away, you can see the white tank under the blue shirt, but when she turns and walks into the dining room to talk to her mom, you can't see the white shirt. When she hugs her mom and leaves the house, the white tank is visible again. She doesn't adjust it in the scene.
Continuity mistake: At the soccer game when Viola removes her wig and she fluffs out her hair, in one shot the wig is in her hand and the next it's gone.
Continuity mistake: When Viola is talking to her mother at the carnival she says completely 'okay, have a good carnival' before turns away. In the next shot, you can see her still saying 'val'.
Continuity mistake: In the scene at the beginning when Viola is walking up to her house and Monique stops her, when she turns around you can see the tip of her ear through her hair and then when it comes back you can't. It changes throughout the scene.
Continuity mistake: In the scene with Olivia and Viola; after Olivia asks Duke out and they walk out side to the bleachers, when they sit down the shadow behind them is different from when they stand up.
Continuity mistake: In the scene at Cesario's when Amanda Bynes comes in and tries to impress Duke and his friends, Duke's hair is noticeably shorter in this scene then in any other. This is proven in the commentary.
Continuity mistake: When Viola is changing into her boy clothes when she's on the carnival ride, she puts her clothes on over her dress, but when she changes back into her girl clothes she takes her dress out of her bag to put it on.
Continuity mistake: At the final kiss scene between Viola and Duke and the end of the movie, they walk towards each other and begin kissing with their hands at their sides. In the next shot, Duke's hand is now on Viola's face, with no time to move it between shots.
Continuity mistake: At the carnival, when Duke and Justin get into a fight and Viola jumps on them, the three of them fall into a popcorn machine. Viola's mother then comes running through the crowd to see what the commotion is. There is a shot from behind her shoulder of her pushing through the crowd into the clearing, then the next shot is of her from the front, where she is pushing through that crowd into the clearing again. The people in the crowd also change.
Continuity mistake: Right before the game between Cornwall and Illyria, Duke and Justin are facing off and flipping the coin. In the far shot Justin only has his left glove on. But when the camera comes in close and Justin punches his chin, he has two gloves on. He doesn't put it on in the scene.
Continuity mistake: In the cafeteria scene, when Viola/Sebastian sits down and knocks her Pepsi over, notice the apple juice and napkin. It is near the top right corner of the tray. In the next shot, it is almost beside the Pepsi, above the tray.
Answer: A. The music supervisor wanted a cover instead of the original. B. It's sometimes cheaper to pay for the rights to a cover than the original song.
Grumpy Scot