Twilight Sparkle and her friends meet Cody, his sister Abby, their best friend Marcella, and their baby brother Fig, who are dropped off by their parents for a visit at their grandparents' farm. Cody hits a basketball by accident while Abby and Marcella laugh and rub a Barney doll in his face. Cody, Rainbow Dash, Scootaloo, Trixie, Lightning Dust and Gilda lose their patience and start a game of keep-away. Cody then hides the Barney doll in the shower and it turns into Barney the purple dinosaur. Cody and his buddies refuse to believe in Barney, claiming that imagination is just for kids and that "real dinosaurs don't talk and real dinosaurs don't laugh."
That night, Cody wishes for a real adventure for that summer, and to do something no one has done before. A shooting star deposits a large colorful egg in the barn, which is accidentally knocked onto a birdseed truck by Cody and is carted off. Barney and Pinkie hear baby Fig needs a diaper change. Barney, the kids and Twilight's group begin their adventure to recover it through a parade. Barney's friend BJ catches it when it almost lands on the ground and breaks. Barney and the gang chase the egg throughout a restaurant, a circus, and fly through the sky on a wooden airplane to continue their pursuit of the egg from a hot air balloon. BJ, Baby Bop, Princess Celestia and Princess Luna arrive just in time to see the egg hatch. After they return the egg to the barn, it finally hatches. Cody comments that the egg looks like a rainbow.
The creature that hatched is a koala-like dream maker named Twinken (to the joy and delight of almost all of Twilight's Adventures team who finds him absolutely adorable) who shows everyone Abby's dream, and then Rainbow Dash's, and then Barney's. Cody, Rainbow, Scootaloo, Trixie, Lightning and Gilda apologize to Barney for being mean to him and all admit they think he's cool. Barney accepts their apology and tells Cody and his newfound buddies he thinks they're cool, too, and they all share a hug. Twinken shows everyone a magical fireworks display which lands in Barney's arms. Barney begins to sing "I Love You" followed by everyone else. Baby Bop gets sleepy, which prompts BJ to decide that they're ready to go home. The film ends with Barney turning back into a doll with Twinken sitting right next to him.
- Princess Celestia, Princess Luna, Shining Armor, Princess Cadance, Flurry Heart, Big Macintosh, Cheerilee, Sunburst, Sugar Belle, Double Diamond, Night Glider and Party Favor will guest star in the movie.
- Pinkie Pie, Princess Celestia and Princess Luna would reveal themselves to be Barney, Baby Bop and BJ's old friends.
- This is an alternate universe version that is very different from Thomas, Twilight Sparkle and Barney's Great Adventure: The Movie.