From Bulbapedia, the community-driven Pokémon encyclopedia.
Ash's Cyndaquil (Japanese: サトシのヒノアラシ Satoshi's Hinoarashi) was the third Pokémon that Ash captured during his travels through Johto. Its Japanese voice actor is Yuji Ueda, and its English voice actress is Kayzie Rogers.
It was first introduced in Good 'Quil Hunting. Ash finds a forest reputed to be populated by Cyndaquil and decides to look for one. Ash was seperated from his friends and chased by Team Rocket into a cave where he found Cyndaquil. After competing with another trainer and Team Rocket for it, Ash was able to capture it.
Personality-wise, Cyndaquil was the "baby" of Ash's group. It started off very weak and lazy, and was easily tired out. In battles, it usually had to wait for the flame on it's back to ignite before using any Template:Type2 attacks. Later, Ash trained it so that it could ignite at will.
Cyndaquil was also very speedy in battle, able to dodge attacks with ease. Arguably, its most notable battle appearance was in the episode Nerves of Steelix. Cyndaquil took down Jasmine's undeniably powerful Steelix. As of now, Cyndaquil is relaxing at Oak's Laboratory, along with most of the rest of Ash's Johto Team.
Unknown to the viewers, Cyndaquil's body color changed, like Corphish's BubbleBeam, over the course of the series. It started off with the top half being royal blue and the bottom half being cream, while later the top half was colored a mossy green and the bottom half was a deep cream.
For more information on this Pokémon's species, see Cyndaquil.