Crustle was first seen as a Dwebble when Ash and his friends were on their journey towards Nacrene City in A Home for Dwebble!. Dwebble was busy making its house out of a rock, which Ash, Cilan and Iris were observing, but three more Dwebble appeared, attacked it and stole its rock, before escaping. Dwebble tried to chase after them but failed. Ash and the others witnessed the scene, and they tried to help Dwebble, but it was scared of the group and attempted to run off. Pikachu tried to assure it, but Dwebble mistook Pikachu for an enemy and attacked him with Slash. Pikachu dodged its attack and Dwebble struck a rock instead. A piece of the rock flew off and hit Pansage on the head. Dwebble felt bad and apologized to him. The gang tried to help it but Dwebble did not want any help and ran off. However, the group helped anyway, with Ash's Pidove searching from the sky and Pansage looking underground with Dig.
Dwebble later returned to the group and Cilan invited it to have dinner with them. During dinner, Pansage collapsed from a fever to which Ash suspected was caused by the rock that hit him earlier. Dwebble becomes overwhelmed with guilt. It later watched over Pansage as it slept and soon fell asleep right beside him. The next day, after Pansage had recovered, Dwebble decided to search for its rock. With the help of the gang, it defeated the other three Dwebble and got its rock back. Later, after the group said their goodbyes and started to walk away, Dwebble began to follow them wanting to be a part of Cilan's team. Cilan, saying that Dwebble was the perfect Pokémon for him, subsequently agreed and captured it.
In Oshawott's Lost Scalchop!, Dwebble fashioned a giant scalchop out of stone for Ash's Oshawott to use in place of the one he lost. At first, the scalchop was much too heavy for Oshawott to carry, let alone use in battle. It took some training, but Oshawott was able to use the scalchop successfully. However, it was destroyed during Ash's rematch with Stephan and his Blitzle.
In Battle For The Underground!, it was let out of his Poké Ball by Snivy when she found it amongst those that Team Rocket had stolen from the Nimbasa Pokémon Center, to help everyone escape from Team Rocket's train, Pikachu asked him to use its corrosive fluid to burn through the door, allowing them all to escape.
In Crisis at Chargestone Cave!, Dwebble was sent out to help battle against Team Rocket. When Woobat launched a Gust attack on it and Excadrill, Dwebble found it hard to hold its ground, but determined to carry on fighting, Dwebble mustered up its strength and began crawling against the Gust. After a few steps, to Cilan's excitement and everyone else's surprise, Dwebble evolved into Crustle. Emerging from the light, Crustle let out a roar, scaring Woobat and Team Rocket. Crustle then revealed itself to have learned Rock Wrecker by using it to block Woobat's Air Slash. Crustle launched another Rock Wrecker alongside Pikachu's Electro Ball at Team Rocket, forcing them to retreat.
In Evolution Exchange Excitement!, Cilan used Crustle in a Tag Battle against Bianca's newly evolved Escavalier and Professor Juniper's newly evolved Accelgor, accompanied by Ash and his Boldore. After missing with X-Scissor, Crustle endured a strong Quick Attack from Accelgor and held back Escavalier's Fury Attack alongside Boldore. Crustle next used Rock Slide, occupying Escavalier while Boldore attacked it, though Crustle's next Rock Slide was stopped by Escavalier's Iron Defense. After Boldore was defeated protecting Crustle from Escavalier and Accelgor's combined Hyper Beam attack, Crustle was able to beat both its opponents by dodging another double Hyper Beam, powering up with Shell Smash and hitting them both with a Rock Wrecker attack.
In Cilan Takes Flight!, Cilan called upon Crustle to participate in Skyla's 'Air battle' simulation. Skyla then predicted that Crustle would be beaten by her Swanna's Water-type attack. Crustle was used to battle Skyla's Swoobat, after Pansage was defeated and won the match with a single Rock Wrecker. Crustle was also able to make quick work of Skyla's Unfezant with a Rock Wrecker and a Shell Smash and X-Scissor combo. Crustle battled Swanna next, the Pokémon Skyla predicted would beat him. After using Shell Smash a second time and colliding X-Scissor with Swanna's Brave Bird, Crustle was defeated.
In Clash of the Connoisseurs! it was sent out to battle Ricard Nouveau's Purrloin. The winner of the battle would be given the honor of picking a Pokémon for Marigold. Despite its Trainer's fear of their opponent, Crustle and Cilan battled to the best of their ability. Crustle defeated Purrloin with a Shell Smash-powered Rock Wrecker attack which then strayed and sent Burgundy, who had been secretly watching the battle, blasting off.
As a Dwebble, it could be described as a little Pokémon with a lot of heart. When its rock that it had worked hard on was stolen from it, it stopped at nothing to try and get it back, despite being outmatched and overpowered. Out of pride, Crustle did not want the dedication it took to make its home to be in vain and it refused to make a second one. It was also been shown to be fearful of humans at first. Crustle is also a very caring Pokémon as seen when it stayed up to watch after Pansage. Crustle seems especially happy to help out the other Pokémon, giving a salute to Pikachu when he asked for its help in Team Rocket's train. After Crustle's first loss in Cilan Takes Flight!, it seemed especially unhappy over the defeat.
On top of all that Crustle is smart and resourceful, using great tactics to win back its home and competently fixing it, whenever it needs fixing.