I interpreted it as the turkey being static on the table until Garfield started to pull on the tablecloth. In my interpretation the lines are supposed to indicate the beginning of movement, but since the turkey started at the edge, it looked like it was thrown there. No, I don’t know why Jon would be sitting idle at a table with a cooked turkey.

One wouldn’t usually throw a turkey in that manner (at least not the people who have served me turkey) but I admit that would probably be no less odd.