Pokémon : S3 | E31 – The Fire-ing Squad!

On the way to Goldenrod City, Ash and his friends stop in a Pokémon Center to send his Tauros back to Professor Oak after using it in the Tauros competition. Oak tells him that Heracross is proving to be a very interesting research subject, thus Ash also leaves Heracross with him. Soon after, Nurse Joy reports that Ash's Pokémon are all in excellent condition. Brock asks Joy to examine him, but a nervous Joy conveniently remembers her duty to examine the Pokémon for something called the Fire and Rescue Grand Prix.

Curious, the group decides to check things out at the nearby stadium. Apparently the Grand Prix is a firefighting contest for Pokémon and their Trainers. Ash decides promptly to enter the contest with his own team, always eager to show off his skills. Misty reminds him that the only Water-type he has is Squirtle, but Ash says he'll just use her Psyduck and Staryu. After an irate Misty complains that he should ask her first, Psyduck pops out. Ash interprets this as an expression of excitement.
(Source: Bulbapedia)