Odie's gold hoop earring switches from his left ear to his right ear eleven times in the special.
The vertical tooth lines on the skull on the hat Garfield is wearing sometimes disappear completely.
When Garfield and Odie are boating to the island, Garfield tosses his peg leg into the water before boarding the boat. However, he has a peg leg again after he is in the boat.
In the very last scene as Garfield turns the TV off and rolls over with his bag of candy to go to sleep, he puts his arm around his teddy bear. As soon as he does so, his arm turns brown, the same color as the teddy bear.
When Garfield is in the river and grabs onto a twig to save him, in that shot, Garfield is being pulled against the flow of the river.