History: Grandpa Longneck was part of Littlefoot's herd when he hatched in the first movie, but became separated from him during the earthquake. He wasn't seen again until the end of that movie and had no lines, but he has been part of every subsequent movie. He was particularly significant in Journey Through the Mists (giving instructions in the event of his death after he fell gravely ill), The Mysterious Island (leading the meeting about the Valley's destruction by locusts and trying to keep the herds together afterward), and Secret of Saurus Rock (where his stories sparked the children's interest in the titular landmark, and his team-up with Doc helped to bring down two sharpteeth).

Of Littlefoot's granparents, Grandpa plays a much more sizeable role in the TV series. In particular, it is shown in Legend of the Story Speakers (Episode 11), that he spent much of his adult life as a traveling storyteller. Apparently this career ended when he chose to settle down with Grandma Longneck, though he continues a private practice in telling tales to the young ones in the Great Valley. His preferred place for doing this is by a volcanic vent, akin to a campfire of today.

Personality: A wisened old Apatosaurus, Grandpa Longneck shoulders the responsibility of looking after Littlefoot with the help of his mate, good humor, and a sensible attitude. Whereas Grandma seems to be quicker to respond to trouble, Grandpa seems to be stronger in planning beforehand, possibly because of his extensive knowledge of legends and stories of the past. He is also something of a community pillar in the Great Valley, often leading meetings on important matters and responses to various dangers. In more personal settings, he enjoys spending time with the little ones and particularly telling them stories. Whatever the circumstances, he always tries to be fair to everyone whether or not they are reasonable or kind – as seen particularly in The Time of the Great Giving (III) when he risked his life to rescue Cera and the obstinate Mr. Threehorn

Family: A storybook of the first movie identifies Grandpa as being Littlefoot's grandfather on his mother's side. Though his daughter is dead, he is seen to have a solid and very positive relationship with his grandson, particularly presented in the book, Me and My Grandpa, where Littlefoot expresses his admiration of Grandpa Longneck and looks forward to one day doing all the things Grandpa does for him.

Grandpa Longneck also gets along well with his son-in-law, Bron. It is indicated that the two of them keep in touch between Bron's periodic visits to the Great Valley or else plan them in advance with great attentiveness, since Grandpa knew Bron would be coming early to administer the Longneck Test in Episode 20 and had the testing sites already prepared. Just how they accomplish this coordination is unclear.

Friends: Grandpa has something of a strained friendship with Mr. Threehorn; although the two of them argue often, they also work well together in times of danger. He also has a young(er) longneck friend named Saro, who admired him greatly in his days as a traveling storyteller. The two of them crossed paths in Episode 11, where Saro expressed disappointment in Grandpa for giving up life as a “story-speaker.” Their friendship was renewed when Grandpa passed the torch on to Saro.