Littlefoot has nightmares involving the "Great Circle", and when he mentions it to his grandparents, they reveal they are sharing the experience, with Grandpa lamenting that they need to go somewhere. Led only by their instinct, they leave the next day. Out of curiosity, Cera, Spike, Ducky, and Petrie follow them. During their trek, Littlefoot is almost killed by a Sarcosuchus in a swamp, but a Supersaurus named Sue saves him and joins him and his grandparents, as she is driven on by the same sense as them. The group is joined by dozens of other Longnecks feeling the same instincts. Meanwhile, Littlefoot's friends are attacked by the Sarcosuchus in the same swamp as before, but they manage to escape. They are also attacked by a Tyrannosaurus afterwards, which they had slept next to after escaping the crocodile. They soon escape into a small cave, and meet Pat, an elderly Apatosaurus.
Littlefoot's herd reaches a large crater where hundreds of Longnecks have gathered. There, he meets his father, Bron, for the first time. After been separated from his mate in an earthshake, he has become guardian to a young Brachiosaurus, Shorty, who becomes jealous of Littlefoot taking all of his father's attention. Meanwhile, Pat shares to Littlefoot's friends that the Longnecks are being driven by a tradition involving a solar eclipse, which was taken as a sign that the Sun will be sent crashing down into the Earth. Every solar eclipse, Longnecks from all around the world gather in one location to stretch their necks up and "catch" the Sun, so they can propel it back up into the sky. Soon after, Pat steps into a pool of magma, which scalds his leg, but he is still able to move.
On the day of the eclipse, Littlefoot wakes up to see Shorty traveling over the crater walls and running away, out of spite for being ignored by Bron. He catches up to Shorty and convinces him to stay; the two reconcile and agree to see themselves as brothers. Moments later, as Littlefoot reunites with his friends, an orange-brown colored Sharptooth attacks the group. Pat defends the children but is slowed down by his injured leg. Bron rushes to their aid and defends them from the Sharptooth, and is nearly killed, but Pat returns and saves him. Soon, they both manage to knock the sharptooth unconscious, only for it to be joined by two other Sharpteeth. Littlefoot's grandparents assist in the fight as well and defeat a green individual. Bron fights the orange-brown one again while Pat fights the same gray individual that Littlefoot's friends had encountered earlier in the film. As soon as the three Sharpteeth are defeated, the eclipse occurs, and the sudden darkness scares away the Sharpteeth towards the end.
Littlefoot, his grandparents, Bron, and Pat take their place among the other Longnecks, who have all gathered on top of the crater walls. They succeed in "catching" the Sun, and everyone rejoices as the eclipse ends. With their mission completed, the different Longneck herds depart on their separate ways. Sue departs with an Ultrasaurus. Littlefoot's friends ask Pat to come live with them in the Great Valley, which he accepts. Littlefoot is initially hesitant in leaving Bron, as he is the leader of a migratory herd, but he eventually realizes that he belongs in the Great Valley. Accepting this, Bron leaves with Shorty and his herd, promising to keep in touch with Littlefoot and visit him. Littlefoot returns to the Valley with his friends, grandparents, and Pat.Alec Medlock as Littlefoot
Kiefer Sutherland as Bron
Kenneth Mars as Grandpa Longneck
Miriam Flynn as Grandma Longneck
Aria Curzon as Ducky
Jeff Bennett as Petrie
Rob Paulsen as Spike
Anndi McAfee as Cera
Brandon Michael DePaul as Shorty
James Garner as Pat
Bernadette Peters as Sue
John Ingle as Narrator/Cera's Dad
The music was scored by Michael Tavera with additional music composed by Stephen Coleman. This was the first film in the series that did not use James Horner's original score.
The songs are written by Michele Brourman and Amanda McBroom. The end credit song, "Best of Friends", is performed by Olivia Newton-John. A shorter version of the song "Adventuring" was heard in four episodes of The Land Before Time TV series. This was the fifth time Spike sings; he is heard humming at the end of "Adventuring", even though Rob Paulsen was not credited for performing the song.Adventuring - Littlefoot, Petrie, Cera and Ducky (Alec Medlock, Jeff Bennett, Anndi McAfee and Aria Noelle Curzon)
Me and My Dad - Littlefoot (Alec Medlock)
Bestest Friends (a.k.a. Best of Friends) - Petrie, Cera and Ducky (Jeff Bennett, Anndi McAfee and Aria Noelle Curzon)
The song, Bestest Friends is also a song sung in the End Credits.December 2, 2003 (VHS and DVD)
September 19, 2006 (DVD - 2 Tales of Discovery and Friendship)
August 5, 2008 (Carrying Case DVD with Fun Activity Book - 2 Tales of Discovery and Friendship - Universal Watch on the Go)
The film is known internationally as "The Great Migration", rather than "The Great Longneck Migration". It was the first film in the series to use fully computer-generated dinosaurs.
Even though this film was presented in full screen on DVD worldwide (since that is what aspect ratio the film was created in), the film is matted to anamorphic widescreen (cropping the top and bottom of the image) on a Hebrew DVD in Israel.