"Strong Pokemon. Weak Pokemon. That is only the selfish perception of people. Truly skilled trainers should try to win with their favorites. You know what's important."
After you and Silver have the double battle against Clair and Lance in the remakes, you can go back to Elm's lab and talk to the assistant. He'll tell you that Silver tried to apologize and return his starter, but Elm decided to let him keep it since it had started to like him. Aww.
Walking Pokemon. At high happiness, your Pokemon will dance and sing, hug or cuddle you (even the types that has claws. Ouch) and find small trinkets like flowers to give to you. It's quite heartwarming when a Legendary adores you enough when its happiness is high enough.