The Land Before Time XVI: The Quest of the Sparkling Treestar is a direct-to-video animated musical adventure feature and the sixteenth film in The Land Before Time series.
Littlefoot teams up with his long-lost twin brother Bigfoot in order to defeat a new enemy named Leonard, a former child actor, obsessed with the 1980s, who grows up to become a villain after having his show cancelled following puberty.
Littlefoot and his partner Ali are sent to foil the plans of Leonard, a former child actor from the 1980s who has turned evil. Littlefoot manages to stop Leonard from stealing the sparkling Treestar, but is unable to capture him. As a result of constantly failing to capture Leonard, Littlefoot and Ali are fired from the Great Valley mysteries.
When Littlefoot and Ali return home, Littlefoot and Ali reluctantly tell their friends, Cera, Ducky, Petrie, Spike, Chomper and Ruby of their dismissal, but assure them they will find new jobs. Most of the Tinysauruses leave Littlefoot, despite losing his job. Meanwhile, Ali struggles to adapt to her new role as Cera, Ducky, Petrie, Spike, Chomper and Ruby's new mom. The next morning, when Mr. Thicknose arrives at Littlefoot's home, Littlefoot discovers that he has a twin brother named Bigfoot, who longs to meet him. Shocked to learn he has a twin, Littlefoot confronts his father, who reveals that when she and her husband divorced, they agreed to keep one child each. The family decides to travel to meet Bigfoot, and they are surprised at his immense wealth, the size of the mansion, which Mr. Thicknose attributes to their pig farm business. Meanwhile, the Tinysauruses are arrested for trespassing at a talent show set. Leonard manages to steal the sparkling Treestar again, intending to use it to power a giant robot and destroy the Great Valley as revenge for the cancellation of his show.
Bigfoot reveals to Littlefoot that their mother was a legendary supervillain, whose villainous activities are the real source of the family's wealth. As Bigfoot was dismissed by their mother as a disgrace, he asks his brother to teach him how to be a villain. When Littlefoot refuses to revert to his old ways, Bigfoot takes him on a joyride in their mother's technologically advanced car and the siblings bond. Meanwhile, Ali tries to balance her new tasks as a mom, which she exhibits after turning away a young boy named Sparky who had fallen for Cera in the midst of a traditional cheese festival, while Petrie, Ruby, Ducky, Spike and Chomper stumble into a local tavern and learn from the bartender about a mythical unicorn which lurks in a nearby forest. Littlefoot tries to convince Ducky, Spike and Chomper that unicorns are imaginary, but decides against it to avoid hurting her feelings. The next day, Petrie, Ruby, Ducky, Spike and Chomper set out into the woods to track the mythical 'unicorn', only to find a one-horned goat whom Ducky, Spike and Chomper adopt and name it "Bobby". Meanwhile, the Tinysauruses' longing for Littlefoot motivates them to escape from prison and return to their former master.
Bigfoot convinces Littlefoot to steal the sparkling Treestar, with Littlefoot secretly intending to bring it to the Great Valley mysteries, Despite several setbacks, they manage to retrieve the diamond and are rescued by Ali after narrowly escaping. After finding out Littlefoot's true motives, Bigfoot confronts his brother about his lie. In return, Littlefoot gets mad at him and decides to leave, ending their relationship. Leonard, disguised as Ali, kidnaps Cera, Ducky, Petrie, Spike, Chomper and Ruby, and once again acquires the sparkling Treestar. Littlefoot and Bigfoot resolve their differences and pursue him after finding the real Ali.
With his robot powered by the sparkling Treestar, Leonard terrorizes the Great Valley, intending to send it into space with the use of super-powered gum. Ali saves Cera, Ducky, Petrie, Spike, Chomper and Ruby while Littlefoot and Bigfoot weaken Leonard's robot with the weapons of their mother's car. Littlefoot is knocked unconscious when the car is destroyed, and Bigfoot manages to destroy the robot's core from the inside when Leonard threatens to kill Littlefoot. When Littlefoot recovers, he battles Leonard in a dance fight, using it as a distraction to grab his weaponized key-tar, and defeats him. Having rendezvoused with Littlefoot, the Tinysauruses manage to destroy the gum already covering the city, and Littlefoot and Bigfoot reunite.
Soon afterward, Littlefoot and Ali are reinstated in the Great Valley mysteries and the newly united family celebrate in Littlefoot's home. Ali is acknowledged by the children as their mother. Dru, along with most of the Tinysauruses, steals Littlefoot's airship, with Littlefoot's emblem replaced with a "B" graffiti. Littlefoot and Ali decide to give them a five-minute head-start before engaging pursuit.
- Debi Derryberry as Littlefoot
- Tom Kenny as Bigfoot, Littlefoot's twin brother.
- Tara Strong as Ali
- Stephen Stanton as Leonard, a evil Oviraptor.
- Anndi McAfee as Cera
- Grey DeLisle as Ducky
- Jeff Bennett as Petrie
- Rob Paulsen as Spike, Guido, Mo and Mr. Clubtail
- Candi Milo as Chomper and Sparky
- Meghan Strange as Ruby
- Patrick Warburton as Big Daddy
- Cree Summer as Lizzie and Tippy
- Leigh Kelly as Skitter
- Ashley Rose as Dusty
- Nika Futterman as Rocky and Tricia
- Kiefer Sutherland as Bron
- Tress MacNeille as Mama Flyer and Mama Swimmer
- George Bell as Topsy
- Barry Bostwick as Grandpa Longneck
- Miriam Flynn as Grandma Longneck
- Dorian Harewood as Mr. Thicknose
- Camryn Manheim as Tria
- Elizabeth Daily as Shorty and Rhett
- Reba McEntire as Etta
- Frank Welker as Bobby
- Chris Rock as Oscar
- The film's script and plot are a spoof of Despicable Me 3.
- Littlefoot has all of Gru's places, moves and lines.
- Bigfoot has all of Dru's places, moves and lines.
- Ali has all of Lucy Wilde's places, moves and lines.
- Leonard has all of Balthazar Bratt's places, moves and lines.
- Cera has all of Margo's places, moves and lines.
- Petrie and Ruby have all of Edith's places, moves and lines.
- Ducky, Spike and Chomper have all of Agnes' places, moves and lines.
- The Tinysauruses have all of the Minions' places, moves and lines.
- Mr. Thicknose has all of Fritz' places, moves and lines.
- Bron has all of Marlena's places, moves and lines.
- Bobby has all of Lucky's places, moves and lines.
- Oscar has all of Clive's places, moves and lines.
- Sparky has all of Niko's places, moves and lines.