After Rat tells Pig that he can fly by jumping off of the house, Pig does just that, landing himself in the hospital. When Rat visits, a delirious Pig asks if he flew far. Rat responds in his usual rude, biting manner saying "You dumb pig, you..." before pausing and relenting, telling him that he flew all the way to the Moon.
Another one has Stephan mourning the death of his father-in-law. Since just describing it would do little to get the heartwarmingness of the moment across, here's the dialogue.
Stephen: And now he's gone. And I sit here and wonder... where did he go? Where is all that love? Where is all that acceptance? ... Where is Rick?
Junior: Dad, you haven't wasted every moment of your life just because you haven't caught all the zebras you thought you'd catch. I can think of a million of those moments you didn't waste.
Larry: Oh yeah? Like wheech ones?
[Panel of both laughing, as Larry pushes his son on a swing.]
A strip from around Memorial Day 2003 starts with Zebra and Rat discussing Pig, who Rat dropped off at the bus station for a trip. Rat speculates that Pig may have gone to the beach as that's "what everyone does on these long weekends." The wide shot shows Pig alone at the Vietnam War Memorial, reading the names.
After Larry gets kicked out of the "Li'l Tykes Kid's Club", when he tries to form Club One Guy.
Rat offering Pig a beer after he got dumped by Pigita (again). Lampshaded by Pastis in the treasury it's featured in, when he says he likes to give Rat the occasional Pet the Dog moment to prove he's not a complete asshole.