Every year, as the warm season approaches, a certain tree in Great Valley blooms with pink flowers. Because of the tastiness of these "treesweets", every dinosaur in the valley wants his/her fair share of it. However, because of this tastiness (and the fact that there seems to be only one such tree in the whole valley), there is hardly enough for everyone. Because of this, none may eat any of the treesweets until the day they "reach the peak of their tastiness".
As the film begins, Littlefoot and his friends Ducky, Petrie and Spike are eagerly waiting to nibble the first treesweets. Ducky is about to take one, but Littlefoot quickly tells her to stop and reminds them all that none may take any treesweets until "Nibbling Day". This however, doesn't stop Petrie from flying to the tree's crown and trying to take one. Just then, Cera's father emerges and states very clearly how every dinosaur in the valley has waited a long time to taste the treesweets. As Cera, too, appears before them, she reminds them that she is the one who is supposed to get the first treesweet because she was the one who found the treesweet-tree in the first place, although it was indeed Littlefoot who did it. Cera also teases Littlefoot for being too little to actually reach the treesweets.
Meanwhile, Cera's father is visited by an old friend—a female threehorn named Tria – whom, it seems, he used to have a crush on. She also reveals his name to be Topsy (although it may simply be a nickname). After speaking a while with her, he promises Tria that she will get the first treesweet of the season; which Cera, who appears just in time to hear him say this, becomes very upset about. From that moment on, Cera refuses to make friends with Tria and simply shrugs her off whenever she tries to talk to her. In addition, Cera will turn violent towards her friends should they make any references involving Tria (be it Tria herself or Cera's father's nickname).
Littlefoot, meanwhile, goes off by himself, feeling very down about how "little" he is. As he returns to the treesweet tree, he climbs up the cliff right next to it and tries to reach the treesweets by himself. As he does, he accidentally falls right through the tree and knocks down every single treesweet. Realizing the trouble he is now in, he faints. As he wakes up, he finds himself surrounded by several miniature longnecks. They have eaten all the treesweets and quickly run away once the shocked Littlefoot starts screaming out of fear.
Upon noticing that every treesweet is gone, all the dinosaurs in the valley are standing in front of the tree; many of them, including Topsy, suspecting Littlefoot to be the guilty party. Littlefoot, afraid to admit it was his fault that the treesweets fell off the tree, blames everything on the tiny longnecks. At first, no one believes him, but when they see evidence of tiny teeth marks on a tree sweet, he is believed and everyone starts looking for the tiny longnecks, preparing to drive them out of the valley once they have been found. As Littlefoot and Cera are searching the valley, Littlefoot falls down a pothole in the ground where, it turns out, the tiny longnecks are hiding in. First being afraid of them, Littlefoot flees deeper into the cave; but soon enough, he finds out that the tiny longnecks are not as bad as he thought and befriends them. Upon hearing how difficult it is for the tinysauruses to find food, he promises to help bring them as many treestars as he can every night.
Eventually, Littlefoot feels ready to tell his friends about the colony of tiny longnecks living in the underground caverns. They all get to see the tiny longnecks for themselves, and promises not to tell the adults. Even Cera, who is still angry with her father, promises to keep it secret, mainly because she finds out that she can relate more to them than she would've imagined. Many of the tinysauruses in the colony feel that their leader, Big Daddy, bosses them around a bit too much, though he simply wants their best. As to the reason that he doesn't trust the "bigger" dinosaurs is that they, in his opinion, only seem to think: "Because they're bigger, it makes them more important".
When sneaking off to see the tinysauruses again, Littlefoot and his friends are busted by Topsy. But when he tries to ask them where they're going this time of night, Cera angrily throws the question back at him. Topsy, not wanting Cera to find out about him and Tria, manages to see them off. Just as Tria comes up to him, they spot one of the tiny longnecks. A chase ensues which eventually reveals their hideout. As the grown-ups prepare to block the caverns; Littlefoot, realizing that he must tell the truth, admits that it was his fault that the treesweets are gone, and not the tiny longnecks'. However, just as he's finished, the tinysauruses' cavern collapses, trapping the tinysauruses inside. The tinysauruses escape. The tinysauruses run into two Sharpteeth that chase them and find their way into Great Valley. Meanwhile, Littlefoot's friends are mad at him. They later try to apologize to him for being angry. However, they mistake the Sharpteeth for Littlefoot. The two carnivores lunge at them, causing a chase. Littlefoot shows up just at the right time and saves Ducky just as she was about to get eaten. When all seems lost, the tinysauruses show up and fight the Sharpteeth. The grown-ups of the Valley then show up and drive the sharpteeth back into Mysterious Beyond through a hole. Then they cover up the hole with a large boulder. Nibbling Day finally comes at last.Aaron Spann as Littlefoot
Jeff Bennett as Petrie
Aria Curzon as Ducky
Michael Clarke Duncan as Big Daddy
Miriam Flynn as Grandma Longneck
John Ingle as Narrator/Topsy
Leigh Kelly as Skitter
Tress MacNeille as Mama Swimmer/Petrie's Mom
Camryn Manheim as Tria
Kenneth Mars as Grandpa Longneck/Longneck
Anndi McAfee as Cera/Diplodocus
Ashley Rose Orr as Dusty
Rob Paulsen as Spike/Kosh
Nika Futterman as Rocky
Cree Summer as Bonehead/Lizzie
The music score was composed by Michael Tavera. Some of his rearrangements of James Horner's original themes from the first film can still be heard in two shots of the film (one where Ducky, Petrie, and Spike tell Littlefoot why they are mad at him and the other where the Sharpteeth come out of a cave), but he was uncredited this film, making this film the last time Tavera's rearrangements of Horner's themes would be heard in a Land Before Time film, as Horner died in a plane crash on June 22, 2015. Also, Michael Tavera's older themes from the previous sequels can still be heard in some other shots of the film.
The music that plays in the background when Topsy catches Petrie trying to get one of the blossoms is the booby trap sliding scene music from An American Tail: The Treasure of Manhattan Island.
The songs are written by Michele Brourman and Amanda McBroom. This is their latest and most criticized collaboration, resulting, in some fans' and parents' views, in bad songs and disrespectful messages to children. This was the first time Grandpa Longneck (Kenneth Mars) sings in the series. "Creepy Crawlies" is the only song played in this film that shares its original melody with a different song; it shares its melody with "Stupid Stompers". Some songs played in the film sound similar to the ones from the previous sequels, but do not share their melodies.Creepy Crawlies - Cera's Dad, Tria, Ducky's Mom, Petrie's Mom, Grandma Longneck and Grandpa Longneck (John Ingle, Camryn Manheim, Tress MacNeille, Miriam Flynn and Kenneth Mars)
Girls and Dads (similar to Me and My Dad from The Land Before Time X: The Great Longneck Migration, but in the minds of Cera, Lizzie and the other female Tinysauruses) - Cera and Lizzie (Anndi McAfee and Cree Summer)
If Only (similar to Family from The Land Before Time VIII: The Big Freeze, but in the minds of Littlefoot and Grandpa Longneck) - Littlefoot and Grandpa Longneck (Aaron Spann and Kenneth Mars)
Stupid Stompers (same tune as Creepy Crawlies, but in minds of Big Daddy, Lizzie, and the Tinysauruses) - Big Daddy and the Tinysauruses (Michael Clarke Duncan, Ashley Rose Orr and Cree Summer)
January 11, 2005 - VHS & DVD, the last Land Before Time film ever released on VHS
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 marked the first appearances of Tria, Big Daddy, and other Tinysauruses. They appear again in The Land Before Time XII: The Great Day of the Flyers. It also marked the first appearance of a Utahraptors in The Land Before Time.