Bolt is possibly a white German shepherd. He was adopted by Penny as a puppy, and has a long time rivalry with his toy "Mr. Carrot."
He grew up on a studio set as an extreme method actor: he never knew he was on a TV show, rather he always believed that the danger and his superpowers were real.
After a mishap, he escaped into the real world where he had no powers. After a harsh awakening Bolt learned how to be a real dog on his way back home to Penny. Reunited, they now live in the country together with Mittens and Rhino.