Jon's sudden turn to defeat in the last panel is so fast that it has to mean in the prior panels he is putting on a brave face. I do love the joke in which a man is mired in a situation going badly, and he grins and denies the pleasure cruise is sinking into an octopus pit.
Garfield, more than perhaps any other strip, does not make any pretense of a fourth wall. Here, Garfield does not even try to aim his rude thought for the day at Jon. It is for us. This is eerie in today's strip, because all the communication in this cartoon is not reaching its expected audience. Jon is blathering to Ellen falls only on his cat's ears, and Garfield doesn't even care to share his snottiness with Jon. Three characters are not talking to each other. The fourth, the reader, can only bear mute witness to this scene.