An Appetite for Battle! (Japanese: ハリマロンVSマフォクシー！ダイエットバトル！？ Chespin VS Delphox! A Diet Battle!?) is the 15th episode of Pokémon the Series: XY.
Chespin gets fat after eating so many of Serena's macarons, so Clemont decides to put it on a diet by making an exercise machine and having it exercise through Pokémon Battles, but Chespin is not making progress.
Since it will be night soon, Serena asks others to hurry up to the Pokémon Center. Ash replies they have to camp outdoors, shocking Serena, who, even if was warned by her mom, didn't take any of camping supplies. Clemont decides to lend a spare tent for her, while Bonnie decides to sleep with Serena. Before they go to sleep, the heroes have dinner, made by Clemont. Serena and Ash are amazed by Clemont's cooking, while Clemont replies cooking is like inventing. While Bunnelby collects the Pokémon dishes, Serena gives everyone some macarons as dessert. Clemont serves tea and Serena opens the basket, but there are no macarons. Clemont is shocked to see his Chespin eating the macarons. He goes to get Chespin, who escapes and eats the last macaron, as well as making itself overweight.
Clemont apologises in Chespin's name. Serena claims she can make some macarons later. After Ash and Serena put the tent Chespin bumped into back, Ash has a battle with Clemont. Froakie uses Bubble, so Clemont orders Chespin to dodge, but Chespin is too fatty to move. Chespin goes to tackle Froakie, who dodges. Froakie goes to pound Chespin, who barely dodges, but falls down. Froakie manages to pound Chespin and defeat it. Ash calls Froakie back, while Clemont is humiliated Chespin lost in a disgraceful way. Bonnie decides to have Dedenne battle Chespin, who is warned by Clemont not to underestimate Dedenne's size. Chespin goes to tackle, but falls down near Dedenne, who shocks it. Clemont is displeased, while Bonnie and Dedenne are glad they won.
During the night, as Ash and Pikachu sleep, Bonnie makes an impression of a Caterpie in her sleeping bag, amusing Serena, who mimics a Swadloon. Clemont makes an invention to get Chespin into shape, who wanders off at the source of a smell it likes. Clemont's eyeglasses shine, as he makes a treadmill for Chespin. While he tests it, Chespin wanders off into the forest. Clemont's machine does not stop and explodes. Ash, Serena and Bonnie come out, seeing another of Clemont's machines have been destroyed. However, nobody sees Chespin and think the explosion has startled it. As the heroes search, Chespin stops at some stairs and is taken into someone's house. As the heroes search, Clemont is wondering if Chespin has gone off because it hates him for forcing Chespin to battle on a full stomach. Serena does not believe that and encourages Clemont to continue searching.
The heroes spread out and after a while, Clemont finds Chespin at an old lady's house and is being fed some macarons by the old lady. Clemont sees how happy Chespin is and remembering how he forced Chespin to battle, Clemont leaves the area. He returns back to his friend and admits he left Chespin be with the old lady. Chespin continues eating the macarons, while the old lady hears her husband has returned, so asks Chespin to do a favor for her, making Chespin almost chocking. The old man comes with a trophy he recently won and looks for his wife, Carrie. He finds some macarons, but Carrie takes the macarons off and asks for the old man, Wylie, for a battle. Wylie laughs, but replies should he win, she has to apologize to him for the words he said yesterday. Carrie replies he will have to do to her if she wins with her Chespin, surprising the latter.
Wylie sends Delphox, shocking Chespin. Delphox uses Will-O'-Wisp, which causes a major blast. The heroes see this and go towards the house. Chespin runs off to dodge these attacks. Clemont takes a step, but stops and watches the battle. Carrie asks for Chespin to attack, but wonders if it even can. The heroes watch the battle and wonder if they should do something, but Clemont replies Chespin hates him. Delphox uses Flamethrower on Chespin, but Clemont rushes in and uses the Aipom Arm to stop the attack. He explains this is his Chespin, so Carrie felt she was doing something wrong. Wylie thinks he won, but Clemont decides to finish this battle. Wylie tells he will allow this, while Chespin is determined to fight back. Delphox uses Will-O'-Wisp, but Chespin rolls to dodge. Clemont is certain rolling will exercise Chespin, reducing its weight and allowing it to counterattack.
Delphox uses Flamethrower, but misses, due to Chespin rolling away. Delphox uses Will-O'-Wisp, but Chespin dodges. Due to so much exercise, Chespin is back to normal and tackles Delphox. Clemont high-fives Chespin, who uses Vine Whip, but misses. Delphox manages to hit Chespin with Flamethrower. Chespin stands up and starts to glow with an aura, as its ability, Overgrow, is activated. Chespin uses Vine Whip and hits Delphox hard. Wylie is annoyed by this and goes to order Delphox its strongest move. He orders Mystical Fire, but his back has too much strain and falls down in pain. Wylie admits this was a loss, but Carrie believes this was a draw, since nobody won. Wylie apologises to the heroes for coming into their quarrel, for yesterday he claimed Carrie should lose some weight. Carrie took offense, thinking Wylie thought she was too fat, which started this conflict.
Wylie also decides to share the cake he bought to Carrie to apologise to her. Later, Carrie considers Chespin lucky to have a fine trainer like Clemont. Clemont thought Chespin hated him, but Chespin denies this. Clemont is glad Chespin still likes him. The heroes bid farewell to Carrie and Wylie and continue their journey. Before the night, as the heroes didn't make it to the Pokémon Center, Serena suggests camping out again, as she had made some new Pokémon impressions.
- "Who's That Pokémon?": Delphox (US)
- "Pokémon Quiz": Delphox (JP)