Kuma Blu, aka Kuma, is a Samoyed belonging to First A.D. Kevin Parks and camera operator Jill MacLauchlan. Their previous dog Chiko also appeared on Supernatural.
Although not a character on the show, Kuma makes small appearances in various episodes. He is usually shown walking past Sam and Dean Winchester.
Kuma was originally intended to appear in season 9 episode "Bad Boys" with Aiden Glass (son of writer Adam Glass), but the scene was cut.