What does Darry call Pony that proves that they have settled with each other in The Outsiders?

Darry calls Pony “little buddy,” a pet name usually reserved for Soda.

Darry and Pony have some problems.  In fact, it is Darry hitting Pony when he came home late that caused Pony to run away and end up in the park where the fight started.  Pony always feels that Darry is too hard on him.  After he returns, however, he and Darry start to make up.

When Randy the Soc comes to check on...

Darry calls Pony “little buddy,” a pet name usually reserved for Soda.

Darry and Pony have some problems.  In fact, it is Darry hitting Pony when he came home late that caused Pony to run away and end up in the park where the fight started.  Pony always feels that Darry is too hard on him.  After he returns, however, he and Darry start to make up.

When Randy the Soc comes to check on him, Pony tells Randy that the hardest thing about the trouble he is in is that they might take him away from Darry.  Darry has been his guardian ever since his parents died.  Pony and Darry have had their problems, but Pony does not want to be separated from his brothers.

Darry is a good guardian; he makes me study and knows where I am and who I'm with all the time. I mean, we don't get along so great sometimes, but he keeps me out of trouble, or did. My father didn't yell at me as much as he does." (Ch. 11)

Randy tells Pony that it was Johnny and not him who killed Bob, and Pony gets upset.  He overhears Darry saying to Randy that Pony is mixed up about the incident with Bob.  Pony gets angry, because he doesn’t want anyone to say anything bad about Johnny, and he doesn’t quite understand that Johnny is dead.

After Randy leaves, Darry tells Pony to put out his cigarette because he is concerned that Pony will fall asleep smoking and die.  Pony has spent almost all of his time in bed since the incident.

"Maybe you can be a little neater, huh, little buddy?"

He'd never called me that before. Soda was the only one he ever called "little buddy."

"Sure," I said, "I'll be more careful." (Ch. 11)

This conversation shows Pony that Darry really does care about him.  The combination of the fact that he does not want to be taken out of Darry’s custody and Darry calling him “little buddy” helps him realize that they will be okay.  It is the first step in making up with Darry.