Dawn captured Pachirisu in Twice Smitten, Once Shy!, where it was shown to have a very hyperactive and mischievous personality. She had much trouble catching it, having to accept help from Ash and his Pokémon. She was looking forward to using it in Contests, but due to its behavior and her inability to control it, she felt she had failed Pachirisu as a Trainer and released it. However, she soon realized her mistake and went back to get it, only to find that Jessie also wanted it. Team Rocket grabbed Pachirisu and took it away, but Pachirisu managed to defeat Team Rocket with a powerful Discharge attack and Dawn recaptured it, willing to give it another chance.
Pachirisu practicing for a Contest
In Borrowing on Bad Faith!, Dawn learned that an unofficial Pokémon Contest would be held in a small village as part of an annual festival and decided to compete using her Pachirisu, since it had never been in a Contest before and was in need of gaining experience. In the Appeals Round, Pachirisu suffered from stage fright and was unable to obey Dawn's command. However, after hearing some words of encouragement from its Trainer, it managed to perform its Sweet Kiss, charming the crowd. It used Spark to create beautiful flower shapes and finished the performance with Discharge, which hit everyone in the audience. In the Battle Round, Pachirisu was put against Jessie's borrowed Aipom. Its attacks were dodged one after the other and it was knocked out by a Focus Punch, losing the Contest.
At the beginning of Getting the Pre-Contest Titters!, Pachirisu was seen practicing electricity storage with Ash's Pikachu. It gathered static electricity on its cheeks before releasing it to create a beautiful sparkling show. It then asked Dawn for a reward and she gave it a Poffin, but it was not satisfied and begged for some more. When Dawn refused, Pachirisu used Discharge to give her a bad hair day.
Pachirisu was Dawn's choice for the Appeals Round of the Floaroma Contest. Although it appeared in a graceful manner, it slipped on its tail and went rolling across the stage, crashing onto the judging panel. It panicked and started running around wildly, but Dawn managed to calm it down by tossing a Poffin in the air, the scent getting its attention. It jumped high with an electrified Spark to catch its favorite food and regained its composure. After that, Pachirisu used Discharge to brighten the stadium and Sweet Kiss to create a shower of small hearts, saving the performance and allowing Dawn to advance to the next round.
In A Stand-Up Sit-Down!, Dawn learned from Zoey that the Hearthome Contest was going to be held under the Double Performance rule. She paired up Pachirisu and Piplup in order to train for this kind of performance and develop some new Contest combinations. She told Pachirisu to use Sweet Kiss and Piplup to use Whirlpool, but things didn't go quite as planned as the large whirlpool covered all the hearts from the Sweet Kiss. She also tried to combine Discharge and Whirlpool, but Pachirisu's Discharge was too powerful and it evaporated Piplup's Whirlpool.
With Dawn at the Wallace Cup
In The Electrike Company!, Pachirisu was called out to demonstrate how to use Electric-type attacks properly and help an Electrike that was having trouble controlling its electricity. Dawn asked it to store electricity before using Discharge, but it overcharged and the attack hit Ash instead of the target. Dawn then gave it a Poffin in order to motivate it and this time Pachirisu succeeded, completely destroying the target.
Pachirisu was used in the Appeals Round of the Hearthome City Pokémon Contest along with Piplup in Dawn's Early Night!. The hearts of its Sweet Kiss were encased by Piplup's BubbleBeam and it used Discharge to dissipate Piplup's Whirlpool in a flash of sparkles. Their performance received positive reviews from the judges but it wasn't impressive enough to advance Dawn to the Contest Battles.
In Glory Blaze!, Pachirisu was briefly seen battling a Tauros and a Granbull alongside Conway's Aggron in the second round of the Hearthome City Tag Battle Competition. Together they managed to defeat their opponents and advance their Trainers to the semifinal round.
Pachirisu was also used in the Wallace Cup. It appeared briefly in Pruning a Passel of Pals!, where it was seen battling a Pelipper in the quarterfinals of the competition. It won the match by points and granted Dawn a place in the semifinals.
Similar to Pikachu in Get the Show on the Road, Pachirisu became ill from storing too much electricity in Doc Brock!. It soon recovered, though, thanks to Brock's aid and knowledge as well as the help of Dawn, Ash and the rest of their team of Pokémon.
In Another One Gabites the Dust!, Pachirisu was seen practicing for the upcoming Chocovine Town Pokémon Contest. When it got tired, Dawn decided to give it and her other Pokémon some Poffins. However, Mamoswine tackled her and sent her flying into the air along with all the snacks. While Pachirisu and the others were trying to cushion Dawn's fall, Mamoswine ate the falling Poffins. The loss of food saddened Pachirisu, but it luckily found one Poffin Mamoswine didn't eat. It rushed over to grab it, but a Gabite appeared and stepped on the Poffin. This infuriated Pachirisu, causing it to learn Super Fang and start a rivalry with Ursula's Gabite.
Deflecting Gabite's Stone Edge
Pachirisu was used in the Battle Round of the Chocovine Contest. It quickly made its way to the finals, where it faced Ursula's Gabite. It was hit several times by Gabite's Dragon Claw because its spinning dodge technique wasn't working against the speedy Cave Pokémon. It tried to attack using Super Fang, but Gabite managed to get past its defense by using Aerial Ace. It then used Sweet Kiss, only to Gabite go through the hearts with another Aerial Ace. With two minutes left on the clock, however, Pachirisu was able to make a comeback. It used Discharge from the tip of its tail to completely destroy the Stone Edge shards and went up against a Dragon Rage with a Spark attack, breaking the move. It countered a Dragon Claw with its tail—which was filled with Discharge's electricity—and defended itself from Stone Edge by putting its tail up and creating an electric shield. It went rolling towards Gabite while using Super Fang and cut through Dragon Rage, reaching Gabite and hitting her with its fang. Gabite covered herself with her fins to prevent major damage and the time ran out. Pachirisu won the match by points, giving Dawn her fourth Contest Ribbon.
In Strategy Begins at Home!, Pachirisu was used alongside Piplup in a Double Battle against Johanna's Glameow and Umbreon. They started the battle by using a combination of Whirlpool and Discharge. However, the combination didn't last long as Johanna's Pokémon were able to gracefully dodge it with a double Quick Attack and destroy it with a double Shadow Ball. After that, Dawn had Piplup using BubbleBeam, but Glameow and Umbreon dodged once again. This was part of Dawn's plan, though, as BubbleBeam was meant to build a barrier of bubbles and hide Pachirisu. When Pachirisu came out from behind the barrier, it caught Glameow and Umbreon by surprise and attacked them with a spinning Super Fang. Johanna's Pokémon quickly fought back with a double Attract, infatuating both Pachirisu and Piplup before attacking them with a double Swift and knocking them out.
Pachirisu was temporarily paired up with Mamoswine in Double-Time Battle Training! in order to make a Double Performance using its Discharge and Mamoswine's Ice Shard. However, it was unsuccessful and their combination failed.
At the Grand Festival with Mamoswine
In Regaining the Home Advantage!, Dawn used Pachirisu to lead a Metagross and a Magnezone that were fighting away from the town that was feeling the wrath of their battle.
In Teaching the Student Teacher!, Dawn perfected a new Contest combination called "Ice Chandelier" with the help of her Pachirisu and Buneary. Pachirisu used Discharge while running inside an ice globe created by Buneary's Ice Beam, making the ice shine in a beautiful blue hue.
Pachirisu was used twice in the battling stage of the Sinnoh Grand Festival. Its first battle in the event took place in Opposites Interact!, where it went up against Ursula's Gabite and Flareon alongside Mamoswine. Despite a good start, Pachirisu and Mamoswine soon found themselves struggling to handle their opponents' powerful combinations and were very nearly defeated. However, they managed to pull off Dawn's newest improvised move, Ice Chandelier, and knock Gabite and Flareon out, giving Dawn the win. In Coming Full-Festival Circle!, it was revealed that Pachirisu, together with Piplup, had helped Dawn defeat her opponent in the quarterfinal round, thus allowing her to advance further in the competition.
In Piplup, Pansage, and a Meeting of the Times!, Pachirisu was introduced to Ash, Iris and Cilan's Pokémon. It excitedly approached the group and kicked Ash's Oshawott's scalchop away due to its curiosity.