Thomas' Adventures of Sofia the First: Once Upon A Princess is another Thomas & Friends/Disney Crossover film to be created by 76859Thomas. It will appear on Google Drive or Dropbox in the near future.
When her mother marries the king, Sofia becomes a member of the royal family and moves into their grand palace, with Thomas the Tank Engine, Ash Ketchum and their friends visiting. She attends a preparatory school under the tutelage of fairies Flora, Fauna and Merryweather in order to train for her new role as princess. With the help of a magic amulet that enables her to talk to animals and an appearance from Thomas and Ash's old friend, Cinderella, Sofia adjusts to her new surroundings and tries to form a bond with her initially reluctanct step-sister Amber.
- Sooty, Sweep, Soo, Little Cousin Scampi, Annoying Orange, Pear, Apple, Passion Fruit, Midget Apple, Marshmallow, Grapefruit, Grandpa Lemon, Nerville, Princess Knight, Choppy, Prince Frank, Discord, Sunset Shimmer, Stephen, Bill and Ben, Trixie, Ash Ketchum, Pikachu, Misty, Togepi, Brock, Molly Hale, Celebi, Mickey Mouse, Pluto, SpongeBob SquarePants, Patrick Star, Squidward Tentacles, Sandy Cheeks, Mr. Krabs, The DigiDestined and their Digimon, Alex, Marty, Melman, Gloria, Woody Woodpecker, Ttark, Dumbo, Timothy Q. Mouse, Jim Crow and his Brothers, Chanticleer, Goldie, Patou, Snipes, Peepers, Edmond, Melody, Tip, Dash, Wreck-It Ralph, Vanellope Von Schweetz, Fix-It Felix, Jr., The Bakugan Battle Brawlers and their Bakugan and The Powerpuff Girls (Blossom, Bubbles and Buttercup) are guest starring in this film.
- The Mickey Mouse cartoons, Dumbo, Wreck-it Ralph, The Little Mermaid II: Return to the Sea, Frozen and Sofia the First: Once Upon A Princess were all made by Disney.
- Both Sofia the First: Once Upon A Princess and My Little Pony Friendship is Magic: Series 3 were first broadcast in 2012, the same year as Thomas & Friends: Blue Mountain Mystery was released on DVD and both Pokémon 4Eever and Pokémon Heroes were re-released on Blu-Ray by StudioCanal in the UK.