When the photographer takes a picture of Candace covered in ashes, she has a disgusted face and her hands are at her sides, but in the photo, she is looking shocked and trying to shield herself with her hands.
When the camera zooms out to reveal the Fireside Girls next to Isabella, Ginger's hair is cut short.
When the car crashes into the garage, there should be a hole in the roof where it fell through, but for some reason neither Linda nor Candace saw it.
At the beginning of "The Fast and the Phineas", Candace uses her phone, but at the race, she uses a payphone to call Linda and a photographer's camera to take a photo for no reason.
When the car goes through the car wash, it takes off all the exterior modifications to the car, but Phineas and Ferb also changed the engine and that was not removed.
When Candace turns on the TV to see Phineas win the race, Linda somehow does not hear the TV despite being within an earshot in the next room.
In Candace's photo of Phineas racing, Phineas' eyes are inverted.
When Candace says "That was last week, Mrs. Garcia-Shapiro!", Ferb's big eye is in front of his smaller eye.
Before the race, Isabella is wearing her Fireside Girl uniform; during the race, she's switched to her regular clothes.