In An Egg Scramble!, Dawn battled Lyra in the Johto Festival and defeated her. As a prize, Dawn was given an egg, which was soon abducted by Team Rocket. While it was in Team Rocket's possession, it showed signs of hatching. When Dawn finally got it back, it hatched right in front of her eyes, revealing it to be a Cyndaquil.
It has a tendency to flare up its back when it's happy or when it's showing affection, which Dawn usually ends up getting caught in in the process.
Dawn's Piplup appears to be jealous over the attention that it gets, though this may be attributed to the fact that Cyndaquil wasn't very responsive to Piplup at first. Piplup often attacks it and it in turn fights back, causing frequent squabbles between the two. They seem to be trying to compete for superiority over the other. These fights have stopped in subsequent episodes.
In Gone With the Windworks!, it battled Ash's Grotle and proved to be a strong opponent even though it had just hatched.
In Dressed for Jess Success!, it showed its interest in Contests after watching Dawn practice with her Mamoswine by trying to mimic it with the flames on its back.
In Bagged Then Tagged!, it was used in Dawn's and Ash's tag battle against Lyra and Khoury. It was able to defeat Chikorita with a Flame Wheel combined with Ash's Monferno's Flamethrower.
In Double-Time Battle Training!, it was used in a double battle together with Dawn's Mamoswine. After using the "Flame-Ice" combo, it failed to execute it all of the way and Zoey's Leafeon defeated it, along with Mamoswine with a Magical Leaf combined with Kirlia's Psychic.
Quilava, as a Cyndaquil, along with Mamoswine, were used in the Daybreak Town Contest Double Battle Round along with Mamoswine in Playing the Performance Encore!. Both of them managed to defeat Ursula's Plusle and Minun in the finals earning Dawn her fifth and final ribbon.
In Last Call, First Round!, it was used in the Appeal Round of the Sinnoh Grand Festival. Together with Buneary, they made an excellent combination that put Dawn through to the next round. Later in Coming Full Festival Circle! it battled Jessie in the semi-finals along with Buneary and got Dawn to the finals.
In SS024, it was used in a battle against Johanna's Glameow and Umbreon, but when Piplup and Cyndaquil unleashed their Whirlpool-Flame Wheel combination; the battle was stopped due to them fighting. Cyndaquil then helped Dawn rescue a Piplup and a Chimchar that had escaped from Professor Rowan's lab from a group of Ariados. It became injured when one of them attacked it with Poison Sting. It was able to overcome its injury by evolving into Quilava. It was able to defeat the leader of the group, a shiny Ariados, with its newly learned move Eruption.