In the fifth book when Greg and Rowley reunite and become friends again, which is also a Crowning Moment of Funny when Rowley offers to share a "Best Friends" locket with Greg.
A similar thing happens in the first movie.
The end of the third book. After all of those constant attempts by Greg in trying to prove to his dad, Frank, that he's not a wimp (which usually ended up proving the opposite), being mistaken for Fregley of all people by his crush and being humiliated in front of the Snellas, Greg FINALLY catches a break; Frank actually thinks the "military school" situation over and decides not to go through with it.
Something similar happens with them in the 3rd movie.
The ending of the second movie.
'Not bad, Heffley. Not bad at all.'
Heartwarming, because Angie spends most of the movie commenting on what a jerk Greg is.
In the second movie, Greg and Holly talk at a retirment home, and realize their family lives are similar.
At the end of the third movie as Heathers birthday party is ruined, Holly tells Greg her sister deserved it, then out of no where she holds Greg's hand, likely becoming an official couple.
From the third movie: Rodrick actually hugs Greg after Greg manages to sign him up to play with his band at Heather Hills' birthday party.
Seeing how Rodrick and Greg's relationship has improved since their bonding in the second movie. In the third, they never fight (something that would be near-impossible for their book counterparts) and Rodrick hardly picks on him seriously, even showing concern and stating that "we've got major problems" when he thinks his brother's going to be shipped off to Spag Academy.
In the same film, Greg freaking out when he thinks Rodrick's been driven away in a garbage truck (It Makes Sense in Context) and then hugging his (mildly horrified, trash-covered) brother when he sees him.
In the film: "I think Dorothy deserved it."
In the eight book, Hard Luck, Fregley, the weird guy who doesn't seem to have any friends, gets voted Most Popular by the student body. And it's completely genuine, too. How? After Rowley starts dating, Greg himself is left friendless, and realizes this is how Fregley feels all the time. So, in an act of desperation, he extends the hand of friendship to Fregley. He's just as creepy as he always is...but his strange antics ("chewing" bubble gum with his navel, getting hopelessly tangled in his sweater) endear him to the other guys in Greg's class, and is soon accepted into their social group...leaving Greg friendless. Again. It's nice to know that even Fregley gets a bone thrown toward him every so often.
Greg also gets some: He refuses to steal a science project for several reasons-he knows that it's stealing, and the people responsible put Roderick's project in there for other people to steal. He may be a jerk, but he sure as hell won't steal from his big brother. As well as that, he comforts Rowley after the breakup, and hides Meemaw's ring so Mom's greedy relatives don't start another war over it.
Rodrick finally spends some decent quality time with Greg, blowing raspberries at Sweetie and having fun together doing so. At least they're starting to bond.
It's very subtle, but look carefully in an Imagine Spot Greg has in the same book, when it shows his future family flipping burgers in their backyard. The wife is an older Holly Hills. Awww, he still likes her!
A quick gag in The Long Haul has Rodrick and Greg teaming up to play a prank on their parents in a flashback. Even though they're not nearly as close as they are in the movies, it's nice to see them getting along for once.
When Rowley anonymously admits Greg did the accidental graffiti in Cabin Fever, the principal gives Greg two choices: tell him who the accomplice was and get off scot-free, or stay silent and clean up the paint himself. Greg realizes that since he dragged Rowley into it in the first place, he should be the one to take the fall. That's right. Greg defied Never My Fault. If that's not Character Development, I don't know what is.
In Old School, while at the torturous Hardscribble Farms, Greg admits choking up at a letter from Mom.
Frank offering Greg a lift home in the car. Really, their interactions after Greg finds the maintenance shed, and how Frank started the Silas Scratch story. Greg admits he'd have done the same things and keeps the secret, passing the name on to the next lot of campers.