While Kevin and his mother are driving home from his school shortly after she is fired, they stop in the car. If you look out the window of their car, you can clearly see a Ford truck or SUV from the 1980's.
When Kevin is leaving the office after being caught trying to steal a pass, a crew member's arm can be seen in the right side of the frame.
At 2:27, when Norma kneels to give Kevin his milk, a boom mic is briefly visible at the top of the frame.