Little Bear's Adventures of The Land Before Time V: The Mysterious Island is an upcoming Little Bear/Universal crossover to be made by Hiatt Grey. And is the sequel to Little Bear's Adventures of The Land Before Time IV: Journey Through the Mists.
After a swarm of "leaf-gobblers" devours all of the plants in the Great Valley and reduces it to a barren wasteland, the inhabitants leave to find another place where they can survive until the plants in the Great Valley have regrown. However, the leaf-gobblers have left a path of devastation behind them, leaving no food for the dinosaurs to find. After searching for many days, tension enters the group as Cera's father and Littlefoot's grandfather argue over changing their course, which starts a fight between Littlefoot and Cera. The fight soon breaks up when Cera's father declares that each herd should go its own way the next morning.
Not wishing to be separated, Littlefoot leads his friends away from the adults during the night, intending to find food before they are found missing. They leave a trail for the grownups to follow, and eventually reach the "Big Water". Although they are disgusted by the saltwater, they see a verdant island connected to the mainland by a thin land bridge. On their way, an earthshake occurs, causing it a tsunami that they narrowly escape. They quickly tuck into the plentiful bounty of the island, but are then horrified to discover the tsunami has destroyed the land bridge.
Isolated on the island, they try out Cera's idea to return to the mainland by using a log as a boat. The plan initially works well, despite Cera suffering seasickness and Petrie being too terrified of the Big Water to act as lookout. However, a Cretoxyrhina attacks, and in the confusion and fright that follows, they end up on the island again. That night, they remember their families, while the herd, who discovered the children were missing and followed the trail, sleep on the beach on the mainland, worrying for their safety.
The next morning, the children wake up to the shadow of a Sharptooth. They take off, but find themselves cornered by high cliffs. They huddle together when the Sharptooth approaches, only to find that it is Chomper, a young Sharptooth who hatched in their care before returning to his parents, and who has learned how to talk like the children. Chomper hides the children from his parents in foul-smelling plants, and provides them with leaves upon their request. However, an overcautious Cera openly distrusts Chomper because he is a Sharptooth, which saddens him, and he departs. Littlefoot follows him and apologizes, but is interrupted by Chomper's mother. Littlefoot watches as she nuzzles Chomper, then leaves, and is intrigued by her display of love to Chomper.
Meanwhile, a Giganotosaurus living on the island finds and chases the children. Chomper and his parents intervene, and they battle the Sharptooth near the edge of the island. The Sharptooth eventually falls into the Big Water and takes Chomper with him, much to his parents' shock. Littlefoot dives in to save Chomper while the Sharptooth is swept away by the current. An Elasmosaurus named Elsie appears, saving Littlefoot and Chomper from drowning. She returns them to the island, where Chomper's parents promise never to harm the children. Cera realizes and accepts that not all Sharpteeth are so bad and monstrous as she thought. Elsie offers to take them across the sea, so Chomper and his parents bid them farewell, promising to see them again. When back on the mainland, the children find that the herd found a lush, green, little sanctuary on the shore to stay in until the Great Valley becomes fertile again.
- Team Griffin/Eeveelution, The Griffin Family, Vinny Griffin, Glenn Quagmire, Cleveland Brown, Joe Swanson, Doug Funnie, Skeeter Valentine, Roger Smith, Bender Bending Rodríguez, Minerva Mink, Master Shake, Meatwad, Frylock, Pazu, Sheeta, The Crystal Prep Girls, Wubbzy, Widget, Walden, Daizy, Natsu Dragneel, Lucy Heartfilia, Gray Fullbuster, Erza Scarlet, Wendy Marvell, Happy, and Carla guest star in this film.
- The storyline concludes in Little Bear's Adventures of The Land Before Time VI: The Secret of Saurus Rock.