Inside the car as the group approaches Aunt Sally's Pecan Pralines, Lucy is wearing a light-colored coat. When she gets out to read the sign on Aunt Sally's door, she's dressed in dark-colored clothes, then back in the car, she has on the light-colored coat again.
Ethel says the mattress on the bed at the cabin is "just like ours [hers and Fred's] at home" and then they go through a routine of getting into bed to which Ethel claims to do every night. Both is these things imply Ethel and Fred share a bed at home, but the few times we've seen their bedroom they've had separate beds.
When the car is outside the motel, it has no windshield nor window glass other than the vent window, and the headlights have a dull, white covering, probably to eliminate glare or reflections from studio lights.