Yuna's New Sibling Part 1 is the nineteenth episode and part one of the fifth season finale of Yuna's Princess Adventure.
Prince Hiro and Princess Luna are expecting a newborn foal and Princess Yuna and Princess Snowdrop are excited about being big sisters, Then there was a Prophecy that a newborn foal of it's royal blood that will be the heart of the balance of Good and Evil and Aku and Lothor wanted to destroy the Prophecy, Now it's up to Princess Yuna, Prince Dusty Crophopper, Princess Snowdrop, Princess Skyla, The Mane 6's Foals, Willow Apple, Pound Cake and Pumpkin Cake, Tigatron, Airazor, WALL-E, EVE, The Alliance of 16, The Mixels, Wheelie, Brains, Silverbolt and Blackarachnia to stop Aku, Lothor and thier henchmen with some help from the Ninja Power Rangers and Ransik and his Alliance.
Dusty the best Prince and racing plane ever!
One day, Prince Dusty Crophopper was racing with Princes Yuna and the other Planes and Dusty won, Everyone and Everypony looked up to hime as the best Prince and Racing Plane of all in Equestria.
Racing Practice/Dusty's gearbox overheated/That night/FIRE!
That afternoon, Dusty was on his Racing Practice with Airazor and EVE, Suddenly, Dusty's gearbox was starting to overheat, So he decided to take a brake until it cools off, Later, That night, Dusty was in for a surprise by Yuna, That Prince Hiro and Princess Luna are about to have a baby foal, Suddenly, there's a fire at Sugarcube Corner, Dusty's gearbox as cooled off and ready to put out that fire with Blade Ranger, Lil' Dipper, Windlifter, Cabbie and the Smokejumpers by his sides.
Meanwhile, Aku was waiting for very long time to break free from his prison cell, When Lothor and his henchmen, Zurgane, Choobo, Vexacus, Motodrone and Shimazu came, Choobo used his sleeping dart to put Cerberus to sleep and Zurgane and Vexacus break the orb and free Aku as they're going about planning for revenge against The Ninja Power Rangers and Samurai Jack and his friends, Unnoticing Marah and Kapri /spied on them and left to warn Cam and the others.
Hiro and Luna's story of Aku
Back at Canterlot, Princess Yuna looked around the Throne Room and saw the glass that shows Princess Sunset Shimmer and the Redeemed Maleficent defeated Aku and send him to Tartarus, Yuna asked her parents, Prince Hiro and Princess Luna about Aku and they explained everything about him.
Luna's Baby Shower
Later that day, A Baby Shower was celebrated in honor of the arrival of Prince Hiro and Princess Luna's newborn foal Yuna and Snowdrop were excited to become big sisters.
The Prophecy/Aku's deal
During the party, Shane, Tori, Dustin, Hunter, Blake, Cam, Marah, Kapri and Sensei Kanoi arrived with Ransik and his Alliance and warned Princess Yuna and her family and friends about the Prophecy that Lothor and Aku wanted to destroy. Meanwhile, Lothor and Aku made a deal that they'd help each other with their revenge against The Ninja Power Rangers and Samurai Jack and his friends by destroying the prophecy they don't want it fulfilled as they gathered Tirek, Queen Chrysalis and King Sombra and his family. Back with Yuna and her friends, Yuna fitted Dusty with a warning light for overheating and he told her not to worry and he'll be fine and he will be careful and they trust each other's instincts.
Journey to Manehattan
So, Yuna, Dusty Skyla, Snowdrop, the Mane 6's Foals, Willow Apple, Pound Cake and Pumpkin Cake and their Guardians arrived at Manehattan as they meet up with Blade Ranger, Lil' Dipper, Windlifter, Cabbie, the Smokejumpers, Maru, Samurai Jack, Sensei Kanoi, The Ninja Rangers and Ransik and his alliance to make sure the prophecy comes true and Stop Aku, Lothor and their Gangs.
Giving Dusty pontoons
Later, Ransik, Nadira, Jindrax and Toxica gave Dusty his pontoons to be ready for this dangerous mission to stop Aku, Lothor and their gang and fulfill the prophecy.
Later that night
Later that night, Dusty wanted to show Snowdrop everything about how he became a firefighter after Yuna learned from him. Snowdrop learned that Blade Ranger is a TV Star, Blade Ranger explained to her that it was a long time ago when his partner Nick Loopin' Lopez died.
Luna's in labor
At Canterlot, Princess Twilight Sparkle, Princess Sunset Shimmer, Princess Trixie and their friends were helping Prince Hiro, Princess Celestia, Shining Armor and Princess Cadance watched over Princess Luna when Rod "Torque" Redline, Scorpan and Star Swirl the Bearded arrived and warned them that Aku, Lothor and their gang are on their way and they've come to help protect Luna, Suddenly, Luna's contraction has started and she's going into Labor.
- This episode is a mixture of Planes: Fire & Rescue and Twilight's Kingdom Part 1 and 2.
- Music score - Planes: Fire & Rescue Main Tites (from Planes: Fire & Rescue)
- Music score - Propwash (from Planes: Fire & Rescue)
- Music score - Out of Production (from Planes: Fire & Rescue)
- You'll Play Your Part -
- Music score - Fire! (from Planes: Fire & Rescue)
- Music score -
- In The Dark Of The Night (Song) - Aku
- Music score - An All New Mayday (from Planes: Fire & Rescue)
- Music score - Sad Mayday (from Planes: Fire & Rescue)
- Still I Fly -
- Music score - Pontoons (from Planes: Fire & Rescue)