Bart the Bear (born 2000), nicknamed "Little Bart", is a trained Alaskan Kodiak actor-bear. Born in 2000, Little Bart is named after the (unrelated) Bart the Bear, who starred in several major films, and who died the same year that Little Bart was born.
Little Bart has appeared in Dr. Dolittle 2, CSI, Scrubs, and Into the Wild.
Little Bart appears in episode 7 of Season 3, the aptly named "The Bear and the Maiden Fair".
Because there are various legal restrictions on international transport of large animals such as bears, Little Bart's appearances were filmed in Los Angeles, USA. As the in-episode guide explains, the sets and actors were still in Northern Ireland, and never filmed in Los Angeles. Rather, a stunt man in a green-screen suit stood in for the bear on-set in Northern Ireland so the actors would have the proper eye-line, while the actor-bear was filmed in his sanctuary in Los Angeles, and his trainer walked him through the required motions for the scene. The actor-bear's footage was then digitally integrated into the shots with the human actors.