Piplup in his debut episode
In Following A Maiden's Voyage!, Piplup got into a fight with the starter Chimchar when it stole the last of his food. He caused chaos by using Bubble Beam inside Professor Rowan's lab and then fled in hot pursuit of the Fire-type Pokémon. While chasing Chimchar, Piplup got stuck in a web created by an Ariados. Seeing the situation, Dawn, who had been given the task of finding the runaway starters, came up with a plan to make Ariados destroy its own web, freeing Piplup and making him land safely in her arms. However, Ariados returned accompanied by several of its species and attacked them, leading Dawn and Piplup to work as a team to escape from the attack. Having fought the wild Ariados off and returned to the lab, Dawn chose Piplup as her first Pokémon saying their journey together had already begun.
Piplup battled Nando's Budew in Dawn Of A New Era!. He started the battle with a Peck attack but Budew dodged easily and used Bullet Seed. He managed to avoid the glowing yellow seeds and use Bubble Beam, getting a clean hit. However, the Water-type move had little effect on the Bud Pokémon. When Nando ordered Budew to use Solar Beam, Dawn thought the move would take a while to charge and had Piplup using Peck. To her surprise, the Sunny Day Budew used before the battle was still in effect and SolarBeam charged immediately, hitting Piplup and rendering him unable to battle.
In Like It or Lup It!, Piplup was seen practicing for the upcoming Jubilife City Pokémon Contest. He had a hard time trying to use Bubble Beam while spinning around in the air, getting dizzy and falling down to the ground in each of his attempts. However, after being motivated by Dawn when helping a group of Water-type Pokémon that had their food stolen by Team Rocket, he managed to perfect the technique. During the Best Wishes series, this technique was used again as a variation of Counter Shield in Piplup, Pansage, and a Meeting of the Times!.
With Dawn at the Jubilife Contest
Piplup made his stage debut in Mounting a Coordinator Assault!, where he was used in the Appeals Round of the Jubilife Contest. He came out of a Foamy Seal and used Bubble Beam to keep the bubbles from the Seal suspended in the air before storing up energy for a Peck. The stored energy made his beak extend and he used the Flying-type attack to explode all the bubbles. With this simple yet remarkable performance, Piplup managed to advance Dawn to the Contest Battles.
In Getting the Pre-Contest Titters!, Piplup learned Whirlpool upon seeing Team Rocket escaping with Kenny's Prinplup. He used the new move to absorb Cacnea's Pin Missile, Dustox's Psybeam, and Carnivine's Bullet Seed before launching it towards them, restoring Prinplup's energy and allowing it to free itself. After that, he and Prinplup forgot the rivalry they started earlier in the episode and became friends, working together to send Team Rocket blasting off again.
Piplup was used in the Battle Round of the Floaroma Contest in Settling a Not-So-Old Score!. His first battle in the event was against Jessie's Dustox, during which he used Bide to return double the damage he took from Poison Sting before knocking the Poison Moth Pokémon out with a Peck attack. After that he was seen defeating a Bagon to advance to the finals of the competition. There he went up against Kenny's Prinplup. They both used Bubble Beam to start the battle and their moves collided in the center of the stadium, creating a shower of sparkles. Piplup proceeded with Peck but Prinplup intercepted with Metal Claw, catching and tossing him into the air. Prinplup then used Drill Peck and Piplup countered the attack with Bide. After recovering, Prinplup used Metal Claw but Piplup dodged and used Whirlpool. The large water vortex engulfed Prinplup, costing Kenny precious points, but was ultimately destroyed by a powerful Bubble Beam. Prinplup followed with Mist to cloak the stage before using Drill Peck and Piplup answered with another Whirlpool. The two Pokémon jumped into the vortex and faced off inside it, with Piplup using Peck and Prinplup using Metal Claw. They then used Bubble Beam again and the time ran out. Piplup won the match by points, giving Dawn her first Ribbon.
In All Dressed Up With Somewhere To Go!, Dawn entered Piplup as a Weedle in the Pokémon Dress-Up Contest, an annual cosplay competition organized by the Pokémon Fan Club where Pokémon try to imitate other Pokémon. During his impression, Piplup got a little too excited and used Bubble Beam, a move Weedle cannot learn, thus ruining his chances of winning the event.
In A Stand-Up Sit-Down!, Dawn learned from Zoey that the Hearthome Contest was going to be held under the Double Performance rule. She paired up Piplup and Pachirisu in order to train for this kind of performance and develop some new Contest combinations. She told Pachirisu to use Sweet Kiss and Piplup to use Whirlpool, but things didn't go quite as planned as the large whirlpool covered all the hearts from the Sweet Kiss. She also tried to combine Whirlpool and Discharge, but Pachirisu's Discharge was too powerful and it evaporated Piplup's Whirlpool.
Piplup was used in the Appeals Round of the Hearthome City Pokémon Contest along with Pachirisu in Dawn's Early Night!. He used Bubble Beam to encase the hearts of Pachirisu's Sweet Kiss and his Whirlpool was dissipated in a flash of sparkles by Pachirisu's Discharge. Their performance received positive reviews from the three judges but it wasn't impressive enough to advance Dawn to the Contest Battles.
Piplup was seen battling alongside Conway's Slowking against a Koffing and a Scyther in the first round of the Hearthome City Tag Battle Competition in Tag! We're It...!. Together they managed to defeat their opponents and advance their Trainers to the second round.
In Hot Springing a Leak!, Piplup battled alongside Leona's Swinub against Ash's Chimchar and Brock's Sudowoodo. The battle ended in a draw when all four Pokémon were frozen solid. In A Full Course Tag Battle!, he battled against Roman's Girafarig and Kylie's Drifloon along with May's Blaziken in the Seven Stars Restaurant Tag Battle challenge. Using a combination of Bubble Beam and Fire Spin that trapped their opponents inside it, they were able to win the battle.
Piplup was used twice in the battling stage of the Wallace Cup. He was first used to battle Kyle's Crawdaunt in the semifinal round. Their battle began in Pruning a Passel of Pals! with a collision of Bubble Beam and Sludge Bomb that cost their Coordinators some points. As the battle continued in the following episode, the two Pokémon jumped in the pool and charged at each other, with Piplup using his Whirlpool to trap Crawdaunt in a vortex. However, his move was taken advantage of when Crawdaunt used Surf, sending him backwards. Crawdaunt proceeded with Dark Pulse, but Piplup avoided the attack with his spinning dodge technique and used Bide to absorb the energy from the two purple beams. When Crawdaunt jumped in the air to strike Piplup with a Crabhammer, Piplup released the absorbed energy, hitting the Rogue Pokémon and causing it to fall into the water just as the time ran out. Piplup won the battle on points, allowing Dawn to advance to the final round.
In Strategy with a Smile!, Dawn used Piplup in the finals of the Wallace Cup, where he went up against May's Glaceon. He started with Bubble Beam, but the Ice-type Pokémon dodged and used Secret Power, paralyzing him. The battle proceeded with Glaceon using Ice Shard, which hit the paralyzed Piplup hard. After that, Piplup jumped in the pool to get rid of the paralysis. When out of the water, he used Whirlpool, but Glaceon received the attack with Mirror Coat and returned it to him, sending him flying backwards. Piplup quickly recovered and used Bubble Beam again, this time hitting Glaceon. When the Fresh Snow Pokémon used Shadow Ball, Piplup spun and dodged it. Glaceon then decided to take advantage of the water covering the stage and attack with Secret Power to try and put Piplup to sleep. Despite being hit and sent flying in the air, Piplup was able to spin gracefully and land in a pose, rendering Glaceon's attack unsuccessful. Glaceon fired another Shadow Ball but Piplup used Bubble Beam once more, destroying it. Piplup followed with Peck, but Glaceon dodged and used Ice Shard. The icy projectiles did not hit Piplup, though, as he used Whirlpool to defend himself. With only one minute left on the clock, Dawn and May had the same amount of points. Piplup then charged at Glaceon surfing in his own Whirlpool. Before Piplup could reach it, Glaceon used Shadow Ball to destroy the Whirlpool, creating a curtain of water. Taking advantage of the situation, Piplup came out from behind the curtain and used Bubble Beam, surprising Glaceon, who then used another Shadow Ball. Piplup destroyed the shadowy blob with a Peck attack, creating a dark purple curtain. This time, it was Glaceon who took advantage of the curtain, using Ice Shard to strike Piplup. Piplup used Whirlpool one last time and Glaceon once again countered with Mirror Coat. Both Pokémon were hit by the water from the Whirlpool and the time ran out. Piplup won the match by points, breaking Dawn's losing streak and giving her the Aqua Ribbon, her second Contest Ribbon overall.
While exploring the ferry from Iron Island to Chocovine Town in Cheers on Castaways Isle!, Piplup was kidnapped by Team Rocket and taken to their Magikarp Submarine along with Pikachu. When the sub was dragged away by a strong current, the two Pokémon ended up on an island located in Diablo's Ocean. There, they helped the local Pokémon to collect pieces of rocks to put them around a crystal that fell from the sky one stormy night. When they gathered enough rocks, Team Rocket appeared to capture them again, but Dawn and Ash arrived on the island just in time to prevent this. At that moment the crystal glowed brightly and turned into a Deoxys. Team Rocket tried to capture it, but the mythical Pokémon destroyed their sub, sending them blasting off. After this adventurous day, Piplup and Pikachu returned to their Trainers.
When Piplup was about to train with Dawn's other Pokémon in Stopped in the Name of Love!, he collapsed from exhaustion, worrying Dawn. Soon after, he started to evolve into Prinplup. However, he used Bide to stop the process and collapsed again. As a result, Brock rushed him to the Pokémon Center, where Nurse Joy explained he just needed some rest. Later, when Dawn was talking to him, he started to evolve again. She told him to let it happen this time, but he used Bide to discontinue the process. As she questioned his motives and spoke to him about the pros of evolving, he got angry and fled the Center. Dawn followed him through the woods, but he kept running away from her, angry at her for not understanding his unwillingness to evolve. While running, he got caught in a web. Dawn tried to help him, but an Ariados appeared and attacked her. The attack destroyed the web and freed Piplup, who landed in Dawn's arms. After that, several Ariados appeared and attacked them with Hyper Beam, but Piplup used Bide to send them flying, just like the day he and Dawn first met. Making matters worse, Team Rocket appeared and captured Piplup. While trying to retrieve her Pokémon, Dawn learned that past events have motivated Piplup to stay the way he is. This made Dawn realize that on the day she chose Piplup, he chose her as well. After sending Team Rocket blasting off, they returned to the Center, where Nurse Joy gave Dawn an Everstone to prevent Piplup's evolution for as long as he wants.
In Three Sides to Every Story!, Piplup fell in love with Lulu's Marill. However, a wild Elekid was also competing for her affections. When the three Pokémon got separated from Dawn and the others, Piplup tried to help Marill, but Elekid seemed to gain the upper hand. When Team Rocket appeared and captured Marill, both Piplup and Elekid worked together to save her. Once Marill was saved, she decided to go with Elekid, leaving Piplup brokenhearted.
In Strategy Begins at Home!, Piplup was used alongside Pachirisu in a Double Battle against Johanna's Glameow and Umbreon. They started the battle by using a combination of Whirlpool and Discharge. However, the combination didn't last long as Johanna's Pokémon were able to gracefully dodge it with a double Quick Attack and destroy it with a double Shadow Ball. After that, Dawn had Piplup using Bubble Beam, but Glameow and Umbreon dodged once again. This was part of Dawn's plan, though, as Bubble Beam was meant to build a barrier of bubbles and hide Pachirisu. When Pachirisu came out from behind the barrier, it caught Glameow and Umbreon by surprise and attacked them with a spinning Super Fang. Johanna's Pokémon quickly fought back with a double Attract, infatuating both Pachirisu and Piplup before attacking them with a double Swift and knocking them out.
In An Egg Scramble!, Piplup was used to battle Lyra's Chikorita in the Johto Festival battling exhibition. Despite the type disadvantage, he was still able to defeat the Leaf Pokémon, earning Dawn a Pokémon Egg.
Piplup was used in the Appeals Round of the Lilypad Town Pokémon Contest in Dressed for Jess Success!. For his performance, he used Whirlpool and then Bide. His Whirlpool came straight down on him and joined forces with Bide, causing him to glow an intense blue from the energy reaction. His appeal was praised by the judges and allowed Dawn to advance to the Battle Round.
At the Grand Festival with Togekiss
In Yes in Dee Dee, It's Dawn!, Piplup teamed up with Buneary to perform at the Daybreak Town Pokémon Contest, which was being held under the Double Performance rule. They finished a stunning performance by exploding the frozen bubbles and sending a shower of sparkles down to the crowd, assuring Dawn's progression to the next round.
In Piplup, Up and Away!, Piplup kept getting hit by Ash's Gible's then faulty Draco Meteor. He thought that Dawn was going to stick up for him, but when she didn't he decided he'd had enough and started to walk back to Professor Rowan's lab. Several times he imagined Dawn coming to comfort him, but he got even more discouraged when he found out she wasn't really there. At one point he came across Team Rocket, who were disguised as Pokémon therapists, and told them his problem. They were very moved by his story, so much so that they scolded Dawn for not noticing Piplup's feelings. Later on, Piplup brought Pikachu over to Team Rocket, unaware of their plot to capture them both, which was successful until a wild Rhyperior came and freed them. Piplup then jumped into Dawn's arms and she apologized to him for not knowing how he felt, as did Ash. He then battled against Team Rocket along with Ash's Grotle, learning Hydro Pump in the process.
As in the Wallace Cup, Piplup was used twice in the battling stage of the Sinnoh Grand Festival. In Coming Full-Festival Circle!, he was revealed to have helped Dawn in defeating her quarterfinal round opponent together with Pachirisu, thus allowing her to advance further in the competition. In A Grand Fight for Winning!, he went up against Zoey's Glameow and Gallade alongside Togekiss in the finals. Despite putting several of the techniques he perfected during his training sessions to good use and combining his moves with Togekiss's nicely, he was unable to bring Dawn the victory.
In Familiarity Breeds Strategy!, Dawn gave Piplup a new cheering uniform for him to wear during Ash's battle against Paul in the Lily of the Valley Conference.
In Memories are Made of Bliss!, Piplup threw a tantrum and ran away from the group when he realized that Ash, Brock and Pikachu were leaving, since he couldn't accept the fact. However, Dawn and everyone else consoled him saying they would always be friends to the end.
In SS024, he was used to battle Johanna's Glameow and Umbreon alongside Cyndaquil. However, when they unleashed their Whirlpool-Flame Wheel combination, the battle had to be interrupted due to them fighting.
With his rival, Ash's Oshawott
Piplup came to Unova with Dawn prior to All for the Love of Meloetta!. In the following episode, he was able to reunite with Ash and meet Iris, Cilan, and his new object of affection—a Meloetta that had been following Ash's group since Virbank City. He also socialized with all the other Pokémon when they were brought out of their Poké Balls and found a rival in Ash's Oshawott, who had feelings for Meloetta, too. Later on, he had a battle with Cilan's Pansage, during which he used Drill Peck to send Pansage's Bullet Seed back at him. When the Grass Monkey Pokémon used Rock Tomb, he negated the move using a variation of Counter Shield. After that, Pansage used SolarBeam, but Piplup countered with Ice Beam. As the two beams collided, they rose into the sky and exploded, creating a beautiful fireworks display. This left Meloetta greatly impressed, causing it to disrupt the battle and start dancing with Piplup.
In Jostling for the Junior Cup!, Piplup was used in the first round of the Pokémon World Tournament Junior Cup against Ramone's Stoutland. Using Drill Peck, he was able to defeat his opponent, thus allowing Dawn to proceed to the second round.
In Goodbye, Junior Cup - Hello Adventure!, Piplup grew sad when saying goodbye to Meloetta before leaving for Johto with Dawn. His rival Oshawott then confronted him one more time, but their contempt soon turned into sadness and they bid a teary farewell. After that, Piplup jumped onto the plane and departed.
He made a cameo in The Dream Continues, When Ash was remembering his traveling companions.