Once in a Blue Moon (Japanese: ヌオーとＧＳボール！？ Quagsire and the GS Ball!?) is the 11th episode of Pokémon: The Johto Journeys.
With Violet City drawing closer Ash and Friends arrive in Cherrygrove City. However a Quagsire steals the GS Ball and Ash tries to get it back only to have him and his friends arrested by Officer Jenny for attempted Quagsire capture in a Preservation area. After explaining the situation she drops the charges and explains about why Quagsire are so revered around Cherrygrove City: They not only find pure, clean water but once a year they take round things, swim with them up the river and send them down the river. The objects taken are returned to their owners and are said to bring good luck, especially to the last round thing floating down the river. Will Ash get the GS Ball back after Quagsire is done with it?
Ash cleans his Poké Balls using a handkerchief and does so for the GS Ball. Misty admits that he is acting as a responsible trainer, to which he responds that a Pokémon Master must care about maintenance. Brock yells lunch is ready, so Ash and Misty go, leaving the Balls laying around. Pikachu notices something in the water and a Pokémon emerges. The heroes see it is a Quagsire, making Misty compliment it and goes to catch it. However, Psyduck emerges from the Poké Ball, who just stands around, confused. Psyduck stares at Quagsire, so Misty gets it, knowing it cannot stand there all day. The GS Ball rolls and Quagsire gets it, then swims away. Ash chases it and sends Squirtle to get the Ball back. Squirtle goes on its back, but slips down in the water.
Squirtle attempts to attack it, though Quagsire bashes it using the tail. Squirtle uses Water Gun, causing Quagsire to drop the ball. Pikachu gets the Ball while Squirtle and Quagsire use Water Gun at each other. Misty goes to catch Quagsire, but suddenly, they hear a whistle. Jenny appears and Brock flirts with her, but stops when she points at the handcuffs, as they have violated the crime by almost capturing Quagsire. Jenny contacts Oak, who apologizes in their name, since they do not know of Quagsire. Jenny tells she'll drop the charges. They explain to the gang the Quagsire are a proof of clean waters, which is why they shouldn't be captured or fought with. Oak tells they are warned, although Ash knows they didn't want trouble. Brock promises nobody will be in trouble and flirts with Jenny, causing Misty to pull him away. Oak reminds Ash of his errand and logs out.
Ash wonders why'd Quagsire want to take the GS Ball. Jenny explains the Quagsire are looking for round things, then go upstream. Next day, the things would float back to their owners, symbolizing pure water and good luck. They notice Quagsire, making Brock think it wants the GS Ball. Ash refuses to let go of it, so Quagsire disappears. The heroes cross a bridge. They notice a Quagsire taking a round part of the end of the bridge and swims away. They agree it is strange they'd take round objects, including the Quagsire. Ash is surprised to see Quagsire, but clarifies he cannot have the GS Ball, but Quagsire is persistent. Quagsire leaps on Ash, so Ash sends a random Pokémon, who is Chikorita. Chikorita attacks, so everyone falls down. Chikorita snuggles with Ash, though Brock thinks it has a crush on him. Quagsire appears once more, so Chikorita attacks it. In doing so, Ash drops the GS Ball, so Quagsire catches it and swims away. Ash tries to chase Quagsire, but Chikorita jumps on his legs to hug him, causing Ash to fall down.
Meowth looks at a round object, making Jessie think that small minds are easily entertained. James looks at the round object, forcing the ball to reveal the location of the twerps. A Quagsire appears and takes the ball. Jessie goes to send Arbok and Lickitung, but the Quagsire take her Poké Balls away, including James'. So, Team Rocket chase the Quagsire. The heroes go to a bridge and see Quagsire is nowhere to be found. Misty thinks if they are lucky the GS Ball will come floating down the river to them. Ash asks if it does not, making Brock think they'll be up the creak, though Misty and Ash know that was a bad joke. Pikachu notices some Quagsire, so they follow them. Team Rocket also follow the Quagsire, making Meowth believe he heard the twerps. Jessie and James admit they cannot stop them, but once they get their Poké Balls back, they will attack.
The heroes notice the pond where Quagsire live, with all kinds of round objects. Brock remembers Jenny told them Quagsire live at Blue Moon Falls, but there is no waterfall present. Ash spots the Quagsire with GS Ball and goes to capture it, but is reminded they promised Jenny not to capture them. Team Rocket see the twerps and plan to capture Quagsire. James does not want to go, but gets forced to. The Quagsire stand still, but Team Rocket appear to catch them all. However, the Quagsire slip away from the cuffs. Since that does not work, Meowth releases a net to capture the Quagsire. Team Rocket float away and search for their Poké Balls, finding them among garbage. Meowth spots the ball he played with and wants them to release them, but Jessie and James pinch him. The heroes follow the balloon, though Team Rocket captures Pikachu. Suddenly, the remaining Quagsire fire some rocks at Team Rocket using Water Gun. Pikachu falls down, so Ash gets him. Ash sends Bulbasaur, whose Razor Leaf cuts the net, making Quagsire to be released. With a giant rock, a Quagsire pierces their balloon, causing Team Rocket to blast off.
The heroes notice Quagsire chanting, then swimming away. The gang tracked them to a waterfall and notice the blue moon. The heroes observe as the Quagsire blow the objects using Water Gun, making Brock believe they have a competition to see who can get their object closest to the moon. Because of this, the water emits sparkles. Ash notices the last Quasire with GS Ball and uses Water Gun, causing it to go higher than the rest. The GS Ball floats down the river, so the heroes go after it. The sun rises as the townspeople see their objects returning back. They notice the last ball, the GS Ball. Jenny sees the gang returning, so she picks the Ball up and gives it to Ash, telling since his Ball was the last one to float down, he'll have the most luck than any of the people. The people clap, so Ash believes he'll win the Johto League. Misty is annoyed as he'll think he is that lucky, but Brock knows he'll be lucky to see he is not that lucky.
- This is the first episode where Ash's Chikorita shows its affection for him.
- This is the final episode of the 90's in Japan.
- The "Who's that Pokémon?" in this episode is Ledyba.
- An instrumental version of "Everything Changes" plays during the ritual.
Officer Jenny's gloves are missing when Brock is holding her hands.