(Japanese: ヒカリのポッチャマ Hikari's Pochama) is Dawn's first Pokémon. She befriended him after saving him from an Ariados's attack, when Piplup and Chimchar had fled from Professor Rowan's lab. He is voiced by 小桜エツ子 Etsuko Kozakura in Japanese and Michele Knotz in English.Piplup initially would not accept food from Dawn—as described in the Pokédex, Piplup are very proud and dislike accepting
food from people. However, he seems to have a large appetite for Pokémon food and does not like having any taken away from him. He shows signs of having a short temper, frequently getting into disagreements with other Pokémon and his Trainer.
Despite his prideful and fierce attitude, he was fairly weak at first. Jessie's Seviper easily defeated the starter Pokémon in his first battle. He has grown in strength since then, helping Dawn catch Buneary in Setting the World on its Buneary, as well as Dawn's Buizel in Buizel Your Way Out of This!.
Piplup is Dawn's main battling partner, used more than any of Dawn's other Pokémon and has helped Dawn win her first two ribbons in Sinnoh. Piplup seems to be very competitive; he will always try to overcome the odds and impress Dawn and get her fullest attention. He often wants to be the first one to start an event for Dawn, and also often tries to peacefully talk to enemies, rather than just attacking them, as seen for example in The Psyduck Stops Here!.
He has been shown that Dawn and Piplup have a close bond with each other. In Staging a Heroes' Welcome!, Piplup helped Dawn recover her confidence by shooting BubbleBeam at her face.
In Strategy With a Smile!, Piplup barely edged out May's Glaceon by only a half a point to help Dawn win the Wallace Cup Ribbon.
In A Breed Stampede!, Piplup was shown to be quite adamant and overconfident. He even tried to stop Piloswine from charging. However, each attempt resulted in being launched into the sky and knocked out. He tried again when Piloswine had already evolved into Mamoswine, but the result was again the same.
In Stopped in the Name of Love, Piplup began the evolution process. However, it soon became clear that Piplup was unwilling to undergo the transformation to Prinplup. After an encounter with Team Rocket, Dawn gave Piplup her full support and acquired an Everstone to prevent his evolution.In Three Sides to Every Story!, Piplup fell in love with a Marill; however, a wild Elekid is competing for the Marill's affections. When the three Pokémon get 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 work together to save Marill. Once Marill was saved, she decided to go with Elekid, and left Piplup brokenhearted.In The Mother of All Battlers! he battled Johanna's Glameow and Umbreon together with Pachirisu in a double battle.
In DP143, Piplup began a rivalry with Dawn's newest Pokémon Cyndaquil after becoming jealous over the attention it was receiving.
Dawn used Piplup in her most recent Pokémon Contest in DP146.