Kenny first appeared in Getting the Pre-Contest Titters!, where it was revealed that he had lost to Zoeyin the final round of his very first Pokémon Contest. He told Dawn's friends several embarrassing stories involving her, which made her angry and caused her to challenge him to a battle, but Kenny ignored her for a battle against Ash and his Pikachu. During the battle with Ash, Kenny used the moves of hisPrinplup uniquely, typical of a Coordinator. He blocked Pikachu's Thunderbolt with ease and left everyone impressed, including James and Meowth, who were watching all the action from a bush. The battle was interrupted by Team Rocket and their attempt to steal Prinplup, but their plans were thwarted thanks to Dawn's Piplup. In the following episode, Kenny competed in the Floaroma Contest. He advanced to the Battle Round and made his way to the finals, where he found Dawn. The two fought a hard battle, but when the time ran out, Dawn was declared the winner. Before bid farewell to her, Kenny said he was happy to have become a Coordinator because that way he and Dawn would battle again.
He made a brief appearance on television in Throwing the Track Switch, where he was seen winning the Sage Town Pokémon Contest with his Prinplup. This victory gave Kenny his second Ribbon.
In Journey to the Unown!, Kenny was revealed to own a Breloom. He was invited by Ash to finish the battle they started in Floaroma Town, but declined the offer saying he was going to see Dialga andPalkia. He decided to battle Ash at the Solaceon Ruins, right in front of the legendary Pokémon statues. Using his Breloom against Ash's Turtwig, Kenny was glad the damage was being kept to a minimum, since it was a battle between two Grass-type Pokémon. He was more focused on showing off the attacks of his Pokémon, just like Dawn anticipated. Ash was struck by a move in particular, Energy Ball, and asked Kenny to teach the attack to his Turtwig. Kenny said he would only do so if he was defeated. Ash agreed, but their battle was interrupted once again when the stairs where Dawn was sitting on began to lift and they had to run to help her. They all ended up inside the Solaceon Ruins, where Kenny became frightened by the illusions caused by the resident Unown. After hearing from Ash that a Trainermust remain calm to pass confidence to their Pokémon, Kenny pulled himself together and began looking for Dawn. While searching for her, he used his Prinplup and Breloom to snap the Unown that kept appearing along the way out of their confusion. Eventually, he found her, and after seeing Piplup convincing the Unown to bring everything back to normal, he left the ruins along with Dawn and the others. Upon leaving, Ash asked him about their battle, to which Kenny replied agreeing to teach Turtwig Energy Ball as long as Ash did not tell Dawn how scared he was at the ruins.
In Team Shocker!, Kenny was seen helping Ash teach Turtwig the move Energy Ball. Later, he participated in the Solaceon Town Pokémon Contest. Using Breloom for the appeals, Kenny impressed the judges enough for them to grant him a place in the second round. He then used Prinplup in the Battle Round, and the Penguin Pokémon quickly advanced him to the finals, where he faced Jessilina. Kenny was determined to win, but Jessilina managed to use his techniques to benefit her Pokémon and this led Kenny to a defeat.
Kenny made short cameos in Pruning a Passel of Pals! and Strategy with a Smile!, watching the Wallace Cup on TV. He then made a cameo in A Breed Stampede!, appearing in Marian's news report about Coordinators alongside Nando.
His next appearance was in Stopped in the Name of Love!, where he, along with Barry, revealed that they are best friends, despite having recently met. He also helped search for Piplup when the Water-type Pokémon ran away from Dawn. In the next episode, he entered the Sandalstraw Contest in hopes of getting his fourth Ribbon. He declared war against Dawn and said he would complete the requirement for the Grand Festival before her. He used his Machoke in the Appeals Round, and the unique performance given by the Superpower Pokémon easily put him in the second round. Using his reliable Prinplup, he made it to the finals, where he found himself up against Dawn once again. After turning the battle into a ping-pong match, Kenny was able to defeat Dawn and her Ambipom, thus winning the Contest.
Kenny entered the Sinnoh Grand Festival in Last Call — First Round!, where it was revealed that his Prinplup had evolved into an Empoleon. During the Appeals Round, he used Empoleon alongside hisFloatzel, and while the appeal started well, the Emperor Pokémon's Flash Cannon proved to be too powerful and Floatzel was sent flying. As a result, Kenny didn't make it past the round, leading to an early exit from the competition. Upset about his loss, Kenny decided not to remain for the rest of the Grand Festival, and after bidding farewell to Dawn and her friends, Kenny left Lake Valor to begin his training anew. He made a brief cameo in A Grand Fight for Winning!, watching Dawn and Zoey compete in the finals.
In Four Roads Diverged in a Pokémon Port!, Kenny was seen doing some training with Jasmine, the Olivine City Gym Leader. He also challenged Ash to a Pokémon battle, and told Dawn he wanted her to travel with him if he won. Using his Empoleon against Ash's Buizel, he was able to win the battle. After that, he told Dawn he would be waiting for her at the city's lighthouse. Dawn didn't show up at the lighthouse, but instead sent him a letter assuring him that as long as they share the dream of becoming Top Coordinators they will meet again. Kenny then set off on his new journey.
He made a cameo appearance in Zoroark: Master of Illusions.
- Piplup → Prinplup → Empoleon
This listing is of the Ribbons Kenny has obtained in the Sinnoh region:
- Unknown Ribbon (prior to Throwing the Track Switch)
- Sage Ribbon (prior to Throwing the Track Switch)
- Gerbera Ribbon (prior to A Breed Stampede!)
- Sandalstraw Ribbon (Old Rivals, New Tricks!)
- Unknown Ribbon (prior to Last Call — First Round!)
Grand Festival ranking
Kenny has competed in the following Grand Festivals:
- Sinnoh Grand Festival - Appeal Round (Last Call — First Round!)
Kenny has competed in the following Pokémon Contests:
- Floaroma Contest - Runner-up (Settling a Not-So-Old Score!)
- Solaceon Contest - Runner-up (Team Shocker!)
- Kenny has a blue Pokétch, the one given to male players in Pokémon Diamond and Pearl.
- Kenny is the only one of Dawn's rivals that didn't progress to the second round of the Sinnoh Grand Festival.