Rhino: If Bolt's taught me one thing, it's that you never abandon a friend in a time of need! When your teammate's in trouble, you go! Not caring what dangers you'll face, you go! Not knowing if you'll come back dead or alive... you go! Knowing how deeply the shrapnel will pierce your hide...
The entire "Barking at the Moon" sequence, where Bolt gets to experience the fun parts of being a dog for the first time in his life.
Mittens at the climax when Rhino uses his hamster ball to prop up the falling rubble of the studio so Bolt can get inside and save Penny, grunting stoically "It is a good day to die!" as his ball starts to crack under the weight. But Mittens wont have any of that. She rushes in, opens the hamster ball, and pulls Rhino to safety. What makes this even more heart-melting is that when we first saw her, Mittens was a cynical, I-look-out-only-for myself loner. Take a look at her now:
Mittens: Not on my watch, rodent!
Mindy From The Network displaying extreme distaste of Penny's Jerkass agent, and speaking to her quietly and like an adult. Unlike the others, she doesn't try to give Penny false hope or act like the bond between her and Bolt is something that can be replaced. She just tells her that people are going to start losing their jobs if they can't start filming again, and asks her to be strong and go back to work. It's a refreshing change.
One of my favorites is near the end where Rhino, who had always believed in Bolt's powers, even after Bolt himself didn't know it, hears Bolt's bark for help, and simply whispers, "It's the Superbark!"
Combines liberally with Tear Jerker, but the moment Bolt resigns himself to the fact that he doesn't know how to save Penny from the fire, he lays down beside her... presumably to die with her. Just the fact that he loved her that much... Thankfully, he remembers the air vent trick shortly thereafter.
The end credits that feature Penny's new adventures with Bolt, Mittens, and Rhino. The animation is so adorable. Also featured at the end is Dr. Calico (or rather, the actor) posing with the show's director and the d-bag agent.