After removing her bra, Genie's bra straps reappear and disappear while she's listening to the "Peace Offering" tape.
When Eddie's mom picks up some of his records, the top record cover changes.
When Eddie's mom is in his room trying to turn off the stereo, she lowers every equalizer potentiometer. When she leaves the room, the potentiometers are back in their original place.
When Leslie is outside the radio station, she starts counting, "One Mississippi, two Mississippi," etc. By the time she reaches the teens, she has dropped "Mississippi." The next numbers she recites are in the low 40's. The next time she is shown, she's at 56 and 57, and the last time she's shown counting (before 90) she's back to 26 and 27.
The spilled Pepsi on the record disappears when Eddie smashes up the stereo.
When Eddie leaves the car that almost went off the drawbridge, one can easily see a jack holding up the back of the car.
When an LP is played, the grooves in the vinyl rotate in a clockwise direction, which causes the stylus to travel from the outer edge of the record to the center. When Eddie is recording Sammi's album to cassette tape (at high speed), the record is rotating counter-clockwise, yet the needle is still travelling towards the center. If the record was turning counter-clockwise, the needle would not do this. It would simply move in the opposite direction and fall off the outer edge.
The movements of Sammi's lips when he is singing in front of the whole school sometimes don't match the Fastway's song heard, revealing that the actor is actually lip-syncing.
In the scene where Eddie is doing his laundry and watching a news report, there is a 5-second shot of the TV screen he is looking at. At the left-hand side of the screen a reflection of the film crew is visible.
A red boom mic is clearly visible during the scene when Eddie's mom is going out the door to a Halloween party with Stan.