Factual error: The very last thing we see before the camera fades to the credits is a waving American Flag. You will notice that the flag is that of the 48 states, not the 50. The stars printed are not in the correct sequence.
Factual error: The dash and stereo of Joe Coopers car and the taxi at the end of the movie are identical even though they are two completely different cars (VW Bug and a Chevrolet Caprice).
Factual error: When Reggie Jackson hit his 3rd homerun in the World Series, it was hit into Yankee Stadium's 'black seats' where there is no admittance, thus Coop could not have caught the ball. And there would certainly not be a big crowd of people up there, as depicted in the movie.
Answer: Jenkins is their dog, the one that attacks him earlier in the film when he walks into the back yard.
Gary O'Reilly
And also attacks him seconds after this conversation.