When Wally pulls his father's car back into their driveway, the front license plate can be seen. All it has on it is the plate number (31844); however, no state or year are on it.
Before Beaver and Gilbert get into the car, we see a side view of it. It's a four door hardtop (no fixed vertical post between the front and rear doors). It also has a sharply curved rear window. When they're in the car, it's a regular sedan with the post between the doors and a standard rear window. The posts between the front and rear seats can be seen as a piece of 1/2" X 4" painted wood.
When Beaver releases the emergency brake, a ratchet clicking sound is heard - the sound of the brake being set.
The clicking sound heard when Beaver pulls the brake release is the sound of a brake being released, not set.
As Wally and the Beaver arrive at Juvenile Traffic Court to answer Wally's citation, a father and son emerge into the hallway, having just seen the judge. They walk around the corner into another hallway, and the actor playing the father apparently stops just as they get out of sight, as his stationary shadow is seen against the back wall for the rest of the scene.