Prior to the start of theDiamond & Pearl arc, Lax was given toDiamond as anEgg and eventually hatched. He first appeared inStagestruck Starly, performing in Diamond andPearl'scomedy routine inJubilife City. Lax managed to ruin the skit by eatingrice balls instead of doing his part of the act, much to Pearl's frustration. Despite ruining the act, the audience found it funny, allowing Diamond and Pearl to win the special prize. Later the two are attacked by a group ofStarly and Lax helps fend them off alongside the other Pokémon.
InDramatic Drapion & Crafty Kricketune II, Lax battled twoScientists that were attacking Diamond and Platinum. At first Lax hid himself and avoided the fight, but eventually joined and attacked withFling while riding onPonyta. Once they became trapped he usesRollout to defeat them.
InProblematic Probopass & Mad Magnezone II, Lax battled Cyrus. Diamond had Lax steal the camera Cyrus was using by activatingPickup. At first, Lax was able to trick Cyrus'sMagnezone by taunting it with the manyBerries hidden in his fur, but is defeated when Magnezone uses itsMagnet PullAbility to pull all metallic objects to it.
Pickup activatedLax battling Fantina's Duskull
InMirages of Mismagius I, Lax is used in Platinum'sGym battle againstFantina. He starts off by fighting herDuskull and defeats it with a singleLick attack and is returned. He is later sent out to fight herMismagius after Ponyta andEmpoleon were defeated. Due to Mismagius's illusions Platinum became unable to give a command and Lax became distracted. With help from Pearl the two get in sync and Lax attacked with Fling, which was enhanced because of anIron Ball, defeating Mismagius.
InLucky Lucario I, Lax is trained onIron Island byRiley alongside Tru andDon. The three start by battling against Riley'sLucario and are quickly defeated due toLucario's speed. Despite the loss Riley points out that the three have amazing defense and work wonderful together. After this Riley took the group into a cave and they are attacked by awildSteelix. Lax and Don manage to hold it down long enough for Tru to attack withCrunch, making the Steelix flee. After the training Lax learned to overcome his weakness in speed.
Lax and Chatler
InChancing Upon Chingling, after Diamond arrived on theGalactic Veilstone Building due to failing to stopMesprit from being captured by Team Galactic, Lax is used to help sneak around the base. Diamond uses Lax'sBerry picking skills to trip and knock out a Grunt so he could steal his uniform to move about the building undetected. Once Diamond was spotted by theAdvanced level Grunt, Lax participated with Diamond's other Pokémon to battle him but proved to be no match for his strength.
InDouble Trouble with Dialga and Palkia VI, Lax was used alongside the other Pokémon to battle against theLegendary PokémonDialga andPalkia. Despite his small size, Lax was able to do great damage to the Dragons with the help of Diamond and Pearl's Pokémon and with a combined technique, they were all able to destroy theRed Chains controlling them.
Like hisTrainer, Lax is gluttonous, lazy, relaxed, and always seen eating. Despite his gluttonous nature, he has been shown to withhold from food, such as when he helps Diamond prepare a meal. He is a slight coward and freaks out at the sight of conflict, sometimes attempting to hide from it.
Despite being a baby Pokémon with little training, he shows considerable stamina and durability. Lax has theability to store many items inside his fur, such asBerries or anIron Ball.
