When you think of Thanksgiving films, you think of Planes, Trains, and Automobiles, and Alice's Restaurant, and to some degree, Miracle on 34th Street, and …what else? There are not very many classic movies centered around Thanksgiving, but if you dig a little, you'll find a few films that aren't exactly fit for prime time audiences. For example, there's Blood Freak, from 1972.
This movie is about a man who turns into a murderous monster with the head of a turkey after he eats a chemically treated gobbler at the turkey farm where he works. Blood Freak has been a cult classic for Thanksgiving for decades now, with many Movie Host shows of the late 70′s onward making a point of screening it at this time of year. The biker who turns into the blood-crazed turkey monster is an Elvis look-alike which adds to the fun. So does the desk-bound, chain-smoking, script-reading narrator who sermonizes about the evils of drug abuse while the movie plays.
There are more lesser-known Thanksgiving movies and shorts in a list at Balladeer's Blog. Link