Abel Marsh says he voted for Harry Truman, but he also says he is 40 years old. Assuming that the movie takes place in 1972 when it was released, he would have been 16 years old in 1948 when Truman was elected, too young to vote in any state of the Union.
In the original theatrical release, when James Garner enters the vets office for the first time, a trainer was visible above the set wall, jiggling his hands to get the dogs in the vet's office to bark.
When Abel Marsh is leaving the dog at the Vet's Dog & Cat Hospital, he climbs in his car and drives in a circle in the parking lot, pausing to look at the lonely Doberman, "Murphy", waiting in his pen for another command. As he brings the car to a stop, the bright gold reflection of sunlight suddenly illuminates his face inside the car. The crew had a hard time training the reflector on his moving face as the car swung around and only managed to pick him up once the car had stopped moving.