Chespin debuted in Mega-Mega Meowth Madness!, where Ash and his friends found it hiding behind a plant and eating macarons. Clemont tried to befriend it, only for Chespin to stab his hand with its spikes and run off with several macarons in its hands. Later, it witnessed Professor Sycamore being captured by Team Rocket and helped Ash and Clemont track the kidnappers by following a trail of macaron pieces left by Dedenne. Once there, Chespin attempted to steal the macarons Jessie left lying around, only to fail and alert Team Rocket to Ash and Clemont's presence.
After Team Rocket unleashed their Mega Mega Meowth, Chespin was saved from being crushed by the mecha by Clemont, which caused the two to bond a little. Chespin helped Clemont stop the rampaging machine by pulling out its plug, only for Team Rocket to use an alternate power source to continue fighting. Having no choice, Clemont and Chespin battled the mecha, only for all of Chespin's attacks to fail. Even when teamed up with Pikachu, the mecha suffered no damage. However, Blaziken Mask's Blaziken saved the day by weakening the machine with Flamethrower, allowing Chespin and Pikachu to finish it off and send Team Rocket blasting off.
Later, Chespin revealed that it wanted to join Clemont's team as it watched him leave Professor Sycamore's lab. Clemont accepted Chespin's request and was given Chespin's Poké Ball to recall it.
In An Appetite for Battle!, after stealing some of Serena's macarons, Clemont became concerned with how Chespin was out of shape from eating so much. To work off some of the weight, he had Chespin battle Froakie and Dedenne, but it lost to both due to its weight. Later that night, Clemont made a machine to help Chespin out, but Chespin walked off into the woods after smelling some food being cooked. Chespin wandered into Carrie's house and was taken in for the night. Much to its delight, there was plenty of food for it to eat. Later that day, it had a battle with Wylie's Delphox. Chespin barely avoided Will-O-Wisp and was about to be hit by Flamethrower, but Clemont stepped in and blocked the attack. Clemont and Chespin then teamed up to battle Delphox, using its rounded shape to roll and dodge attacks until it lost weight, this allowed Chespin to move much quicker and hit it with a Tackle and Vine Whip. However, Chespin was hit by a powerful Flamethrower, which led to the activation of its Ability, Overgrow. Chespin then hit Delphox with one more powerful Vine Whip. It was then about to be hit by Delphox's Mystical Fire, but the battle was stopped due to Wylie experiencing pains in his waist.
In Forging Forest Friendships!, Chespin was used in a Double Battle with Bunnelby against Hawlucha and Froakie. Due to an argument between Froakie and Hawlucha, Clemont's Pokémon had the upper hand, but Froakie used its speed to trick Chespin's Pin Missile into hitting Bunnelby, knocking it out. After this, Froakie and Hawlucha started to fight, ending the battle. Later, it was shown that Chespin had eaten all of Serena's Poké Puffs when she tried to give them out.
Chespin's rivalry with Pancham
In Battling Into the Hall of Fame!, Chespin was used in a Team Battle along with Pikachu and Fennekin against Shauna's Bulbasaur, Tierno's Squirtle, and Trevor's Charmander. Chespin and the others got at a disadvantage due to their opponents great teamwork. When Shauna's Bulbasaur fired a Solar Beam at Pikachu, Chespin used its Vine Whip to tilt Pikachu up, giving Pikachu the opportunity to defeat Charmander. Chespin then used Vine Whip to counter Squirtle's Rapid Spin, while Pikachu defeated a defenseless Bulbasaur. Eventually Pikachu also defeated Squirtle giving Ash, Serena, and Clemont the win.
In Pathways to Performance Partnering!, after eating all of the Poké Puffs, Chespin had a continuous quarrel with Serena's Pancham. During their quarrel, they accidentally disturbed Nini training with her Smoochum and Farfetch'd for her upcoming Pokémon Showcase. Later, a disguised Team Rocket then appeared and managed to steal Pancham, Chespin, Fennekin, Smoochum and Farfetch'd. While trapped inside of a ball, it and Pancham again quarreled causing them to escape from the ball. However, Team Rocket quickly found them again and managed to injure Fennekin, Smoochum and Farfetch'd forcing Chespin and Pancham to work together. Eventually they got reunited with their Trainers and together Chespin and Pancham defeated Team Rocket. Although it seemed the two finally understood each other, Chespin and Pancham quickly began to quarrel again after the battle.
In Adventures in Running Errands!, the group arrived at a Pokémon Center to shelter from the rain. A leak in the roof, however, caused the center's machinery to short-circuit. While Clemont was fixing the machine, he had Chespin and Bunnelby run an errand to buy a machine part. Chespin was given a purse with a letter on which the part's name was written. While heading towards the shop, a wild Fearow snatched the purse from the duo. The two eventually managed to get the purse back and escape from the Fearow. While continuing their errand, Chespin and Bunnelby got attacked by Team Rocket. They managed to hold their own against Inkay and Gourgeist. When Gourgeist attacked with Shadow Ball, Fletchinder arrived and blocked the attack with Steel Wing, followed by Ash and Noibat. Despite being told to stand back, Chespin and Bunnelby continued to fight Team Rocket themselves and managed to blast them off. Chespin and Bunnelby then finished their errand, giving Clemont the last part to fix the Pokémon Center's main system.
In A Watershed Moment!, Chespin walked across a barren land along with Clemont trying to keep the tired Gym Leader from collapsing before they came across Robon. As Chespin along with the others observed the robot planting seeds, they got surprised by a Seed Bomb attack coming from an angry Chesnaught looming from large a rock before suddenly attacking them. Chespin attempted to go against its fully evolved form, but backed down just as quickly as the Chesnaught began chasing it around. After managing to get away, Chespin pointed out a rundown building to the group that once belonged to Chapman. After assessing the situation, the others and Chespin decided to help out Robon and also managed to gain the trust of Chesnaught as well. While Clemont's Luxray used his X-Ray vision along with Ash's Noibat using echolocation to locate a water source, Chespin used Vine Whip to help search underground too, also encouraging Chesnaught to mimic with its own Vine Whip. After a while, Chespin managed to find the source only to be blocked by a large rock. As everyone tried to remove it, Team Rocket appeared captured them. After Chesnaught managed to break the remote control thus freeing everyone, Chespin combined its Pin Missile along with the other Pokémon's attacks to send Team Rocket blasting off. After Robon was fixed and successfully destroyed the rock to let the water flow, Chespin bade farewell to Chesnaught as they headed out.
Clemont sent out Chespin and Bunnelby to combat Team Flare in Coming Apart at the Dreams!. They joined the battle against Bryony's Liepard and Aliana's Druddigon. The two of them, alongside Luxray and Heliolisk, defeated the Team Flare Scientists' Pokémon, allowing Clembot to subdue them and for the team to infiltrate the Lumiose Gym. In the following episode, Chespin battled with Xerosic's Crobat and Malamar, which resulted in victory and allowed Clembot to evict Xerosic from the Gym. Chespin was used again in Forming a More Perfect Union!, where it joined the fight against the Giant Rock. In the next episode, Chespin and the rest of Clemont's Pokémon received medals from Professor Sycamore for their heroic efforts against Team Flare.
In Facing the Needs of the Many!, Chespin was sent out to battle Xerosic again, alongide Ash's Greninja. After countering Crobat's Air Slash with Pin Missile, it dodged Malamar's Signal Beam by having Greninja hurl it at their opponents, allowing it to hit Crobat with an extra powerful Tackle. After Greninja defeated Crobat, Xerosic recalled his Malamar and tried to escape, but was caught by Clemont's Aipom Arm.
Personality and characteristics
Chespin's gluttonous habit
Chespin is gluttonous and often goes after food, especially its favorite macarons. As a result, Chespin would keep the food for itself and refuse to give it back. When caught in the act, it is unrepentant, unless coaxed. Sometimes, it would eat so much food that it would become heavy, as evidenced in An Appetite for Battle!. Its gluttony is usually the source of conflict between it and Serena's Pancham, another trait it shares with Oshawott (who usually ends up butting heads with Ash's Pignite).
Chespin with Bonnie and Dedenne
Despite its gluttonous traits, it is also very courageous, going after Team Rocket and respecting Clemont after he saved it from getting run over by their mecha. It is also shown to be very determined when it repeatedly tries hitting Team Rocket's mecha despite its efforts being met with failure. Chespin tends to be the more vocal of the group and usually displays a very happy-go-lucky attitude. In A PokéVision of Things to Come!, Chespin was shown to enjoy the spotlight and is very confident on camera, unlike its Trainer. First shown in Battles in the Sky!, Chespin has occasionally came out of its Poké Ball for various reasons, such as battling, meeting new Pokémon or wanting to do something. In Dreaming a Performer's Dream! and Pathways to Performance Partnering!, Chespin has shown an interest in performing.
First shown in Pathways to Performance Partnering! and later A Race for Home!, Chespin developed a rivalry with Serena's Pancham and would later get into several quarrels with him. Though in Love Strikes! Eevee, Yikes!, it is shown that Chespin does get along with Pancham most of the time. Another time is when Chespin gave up its food willingly to Pancham in Master Class Choices! to congratulate him.
Chespin also shows an interest in being friends with Serena's Eevee, but its outgoing, spontaneous personality clashes with Eevee's timidness, causing her to flee behind Serena or Bunnelby, and leaving Chespin dejected. Chespin's approach is no longer rejected upon Eevee's evolution into Sylveon, making Chespin overjoyed when she accepted its encouragement for the Showcase.
| Using Pin Missile
| A † shows that the move was used recently, unless all moves fit this case or there are fewer than five known moves.
Below are Chespin and Chesnaught's speaking voices in Pikachu and Meowth's dream in Dream a Little Dream from Me!.