Title panel: This dire possible-Phantom Menace-reference image sort of summates an idea intrinsic to Garfield, unlike most Sunday title panels, which normally have nothing to do with anything. Garfield confidently moves in on his prey with a combination of cat-like hunting skill, human-learned traits, both of which he is abusing: snorklers are not supposed to murder the fish they observe. While he takes visible satisfaction in this, the cosmos are going to collect a hefty fine from the meek and the mean alike. The idea actually plays out in today's strip, too.
Panel 1: Cats have little narrow tongues. While I appreciate Mr. Davis' ongoing effort to demolish standards of feline anatomy at every turn, his depiction of Garfield's tongue always grosses me out a little.
Panel 5: The Garfieldian version of cause and effect has little to do with karma, or swift justice, or even a universal morality meting out punishment and reward in a pattern the characters can understand. But perhaps we can discern a kind of fatalistic irony anyway. What has Garfield done "wrong" today? He fails to look before leaping, literally not checking the wading pool for water. He seeks to sully a neighbor's property -- in Judeo-Christian terms, we might say he is "stealing" -- without second thought. Overcome with excitement, he showboats with an overzealous leap, boastful and prideful. But those are normal, petty sins that in the laws of Garfield's universe are not as funny to punish as the self-satisfaction of someone who thinks they have it all figured out.
Buster Keaton's physics often worked on a similar principle: dumb luck will save your life, but any plans will be demolished in the process. Garfield supposes you might also smash your face into a tree. The difference between this lesson and a Chuck Jones Roadrunner cartoon, is that there is nothing harebrained or elaborate about jumping into a swimming pool. The margin for error is small enough, the scene mundane enough, that only Garfield would see it as an opportunity for punishing a character so harshly.
Panel 6: Here was a chance to reward Odie by having him splashed with a pool full of water, or indicating that he is granted some relief by the shade of the pool on his head. No: he just gets a pool on his head.
Also: Garfield jumped into the pool so hard he reversed the color scheme? Bravo.