Doc is a wandering elderly Diplodocus who goes "where the road takes him". He is taciturn, and not forthcoming of his past. In his first appearance, he saves Littlefoot shortly after arriving in the Great Valley, and Littlefoot idolizes him after getting the idea that he is the legendary "Lone Dinosaur", who according to a story he heard from his Grandpa, saved the Great Valley from a particularly powerful Sharptooth long before; Doc's own statements about having visited the Great Valley before, as well as a large scar on the right side of his face resembling an identical one that the Lone Dinosaur received from the Sharptooth he defeated, support Littlefoot's ideas. When the Great Valley residents accuse Doc of bringing a recent string of misfortune to the valley (Including, among other things, a tornado), Littlefoot defends him to the point of putting him above his own grandfather to the surprise of the adults. At the end of the film, after Doc and Grandpa Longneck defeat a marauding Brown Allosaurus and a Tyrannosaurus Rex together, Doc leaves the valley. Littlefoots begs him not to go too far, in case the valley may need a hero again, but Doc states that he already has a hero, his Grandfather.