Popplio is very playful and it likes to make bubbles for fun or claps its hands. At first, it is afraid of people, but under Lana's care, it becomes friendlier and likes to stick with humans.
Lana was using a Poké Ride Lapras and found saw several members of Team Skull intimidating Popplio. Lana had Lapras freeze the grunts with Ice Beam, then came to rescue Popplio. After taking it to the Pokémon Center, Lana fed Popplio and the two have been inseparable ever since.
Lana was fishing with Popplio. Once they saw Ash being startled by a Bruxish, they both started laughing, with Ash laughing as well. Later, Lillie watched over Popplio while Lana rode a Tauros along with the other Trial Captains.
Once Ash came to the Pokémon School one day, Popplio made a watery balloon to surprise him, as Lana and others made a surprise party for Ash. Lana also had Popplio race Pikachu. Though Pikachu was quicker than Poppio on land and swam as fast as he could, Popplio was much faster at swimming and won the race. Lana praised Popplio and told it that it was amazing. Lillie later explained to Ash that Popplio could swim up to 40 kilometers per hour.
Popplio was with its trainer, who went with Ash to see what new Pokémon he would catch in the forest. Popplio also watched as Team Rocket appeared, who threatened to steal all their Pokémon, and how they were dragged by a Bewear. After Ash's Pikachu got hurt in a battle against Grubbin, Popplio went with its trainer away to report to Professor Kukui what happened.
As Ash went to school, he saw Lana training her Popplio. Popplio tried to make a watery balloon, but failed and fell in the sea. Once she arrived to school, Lana and Popplio heard that Lillie had a secret weapon for fishing. Popplio clapped and jumped into Lillie's lap. Lillie was terrified, so Lana took Popplio back and both apologized to Lillie. Once school was over, Popplio had a race with Pikachu on the beach and won. After Lana told Ash how she met Popplio, she had it emit water balloons, which splashed and soaked Ash. Regardless, she admitted she wanted to have Popplio make a big balloon so they could travel under sea and meet lots of water Pokémon. Ash was confident Popplio was capable of achieving that dream; Popplio tried to make one, but failed and soaked Ash and Lana. During fishing, Team Rocket stole the group's Wailmer and Lapras. Just as Pikachu freed the Pokémon from the net by using Iron Tail, the Pokémon were to fall on rocks. Fortunately, Popplio managed to emit a giant balloon, which saved the Pokémon, who dived into the sea. After Team Rocket's defeat, the group praised Popplio, who emitted one more balloon and enveloped Ash and Pikachu in it. However, the balloon soon splashed and made Ash and Pikachu fall down.
Popplio was with its trainer when Ash explained the "Litten situation". The class spoke about the Rattata and Raticate problem and found out the solution were Yungoos and Gumshoos. Their yelling startled Sophocles' Togedemaru, who ran in circles and knocked Popplio and Mallow's Bounsweet off the table. Pikachu managed to stop and calm her down, but Togedemaru started showing affection towards him. Popplio, along with its trainer, was at the party to celebrate Ash and his Pokémon's Grand Trial of Melemele Island victory.
None of Popplio's moves are known.
Rikako Aikawa (Japanese)
Eileen Stevens (English)