Oh boy! What a mess!
Panel One a: What are they looking at?
Panel One b: Garfield's legs have mutated and/or atrophied such that I'm not sure he can walk on all fours even if he wants to.
Panel Two a: If Garfield doesn't know that he ate checkers -- clearly he has no visual recognition of checkers-- then why would the word "checkers" trigger his moment of clarity? I would hazard to suggest the strip would work better with no reaction from the cat until Jon asks where the checkers have disappeared to.
Panel Two b: It is one thing to talk to a pet, despite getting no reaction for better than 25 years, because we all do it, and Garfield is more reactive than most. It is another thing to realize you will be sitting at home with your kitty on Saturday night. It is another thing entirely to ask your cat to play checkers with you.
Panel Three a: Woah, jump cut, settle down! I guess Jon went and got the checkers box, set up the board, and returned to precisely the same position, but it's disorienting. I cannot, however, explain why he is consulting the front of the game box to determine the location of his missing playing pieces.
Panel Three b: Somehow this checkerboard measures six squares on the long sides, four squares on one side... and three squares on the parallel side. It's his professionalism that I respect.
Panel Three c: If Jim Davis ever draws Garfield's tongue like that again, I'm gonna barf.