Originally a recurring Pokémon, Krookodile debuted as a Sandile before evolving into a Krokorok. Despite losing to Ash's Pikachu, Krokorok later chose to join Ash's party and later evolved into Krookodile.
As a Sandile, he was mischievous that he caught Pikachu, Axew and Oshawott with his same kind. But he also has a caring side, in which he saved a group of wild Pokémon when he sensed danger. Like Ash's Squirtle before him, he was a capable leader leading a group of wild Sandile to make themselves a bridge and also took a liking to Ash before he joins Ash's team after he evolved into a Krokorok. He also has a desire to defeat Pikachu in battle to make him as his rival and it was his trait that he wanted to face Pikachu in battle head on while trying to follow Ash in his journey in both his pre-evolved forms. Sandile was seen as a calm and determined Pokémon but was also a coward when his sunglasses were either stolen or missing as seen in Dancing with the Ducklett Trio!, and always sided with Ash just to retrieve his sunglasses back from them.
As a Krokorok, he continued to be compassionate and smart, but he became impulsive too, causing a lot of troubles that he didn't think about. But he still maintained his pre-evolved personality when he lost his sunglasses and his desire to battle Pikachu. After being defeated by Pikachu in battle, he became depressed until Ash let him join his team, much to his happiness. When he comes out of his Poké Ball during battles, Krokorok always shows his coolness.
After evolving, Krookodile becomes a fun-loving Pokémon similar to Ash's Squirtle while retaining both his compassionate and strategic side and also enjoys battling other Pokémon especially competitions in the Junior Cup or the Unova League.
As a wild Pokémon
Krookodile first appeared as a Sandile in A Sandile Gusher of Change! where he was given the nickname, the Sunglasses Sandile because of the sunglasses he wore. At the time, Sandile was also the leader of a group of fellow Sandile who all lived near a local spa resort with the Sandile group often causing trouble, all for the sake of getting attention from the owners. He was later revealed that the group was actually attempting to save the other Pokémon in the area because the Sandile themselves knew that in advance that a geyser would soon erupt. With the help of Ash, Iris, and the son of the spa resort owner, Dan, Sandile was able to save the Pokémon. In the end, Sandile was shown to have gained respect for Ash, and as such, began to follow him, presumably abandoning his fellow Sandile or leaving them to serve as guards for the spa.
Sandile returned in Here Comes the Trubbish Squad! where he sought to battle Pikachu. Sandile attacked by randomly using Stone Edge, endangering the lives of a group of young children who were nearby. Both Pikachu and a wild Trubbish intervened as the former use Iron Tail to attack Sandile and finally get blasted off by the latter's Sludge Bomb.
Sandile reappeared in Dancing With the Ducklett Trio!, who is responsible for digging down the hole to make Ash and his Pikachu sliding down the mountain. Both Ash and Pikachu are soon confronted by Sandile whom Ash remembers back when he is trying to save both Pikachu and Oshawott. Sandile wants to battle Pikachu and it was the reason he dug the hole just to battle it which Pikachu confidently agrees. Both Sandile and Pikachu had an equal fight but is soon interrupted by one of the wild Ducklett trio who gets in the way. Sandile scolds it not to interfere until this Ducklett appears as a dimwitted and it checks on his mouth causing him to get cough. To make much worse, the Ducklett manages to tickle Sandile's nose causing him to sneeze and gets his sunglasses. Realizing how mischievous it is, Sandile cries in desperation to get his sunglasses back but the Ducklett hits him with Scold to knock him down temporarily much to both Ash and Pikachu's surprise.
With Ash and Pikachu assisting him, however, Sandile replaces Pikachu in battle after its Electric-type moves got overcharged due to the pink umbrella had thrown at him by the Ducklett trio and was able to beat the Ducklett trio in an handicap despite the type-disadvantage. Pikachu manages to deflect their moves but Sandile ends up getting pummeled by the Ducklett trio with their Steel Wing. When Ash, Pikachu and Sandile had enough of the trio's mischievous ways and its bullying, Pikachu unleashes its electricity due to overcharge but learns Electro Ball from its tail to angrily blasts the Ducklett trio off much to Ash's surprise. As Cilan, Iris, Scraggy and Oshawott reunite with Ash, the Ducklett trio returns to attack only to be blasted again by Pikachu from his Thunderbolt making Sandile reclaims his sunglasses back. After being healed with Pikachu at the Pokémon Center, Sandile finally resumes his battle with Pikachu while being watched by Cilan and Iris. Sandile dominated the battle right from the very beginning by using Stone Edge followed by two Digs making Pikachu take serious damage. Sandile seriously confronts the weaken Pikachu while it evolves into Krokorok. However, Pikachu gained the upper hand by blasting Krokorok off by using Electro Ball to deflect his Stone Edge to sending him flying away.
After a long absence, Krokorok returns at the end of Explorers of the Hero's Ruin!, still harboring to defeat Pikachu while startling Ash, Iris and Cilan.
In Battling the Bully!, Krokorok wants to defeat his rival Pikachu while confronting Ash and the group as they remember him from his previous battle with Pikachu while he as a Sandile evolves into Krokorok and Cilan knows he had been following them on their journey the whole time as a series of flashbacks then revealed that Krokorok had followed the group through various locations, including Nimbasa Town and Nimbasa City and it was also shown that Krokorok had been the one responsible for throwing a pen into a Klinklang during Evolution Exchange Excitement! as the pen he had thrown to Klinklang belongs to Professor Juniper's father, Cecil Juniper.
Krokorok and Pikachu engaged in battle yet again as he manage to use Dig to avoid Pikachu's Iron Tail but he dodges his ambush while using Crunch. Both Pokémon being sent flying off after they collide with both Pikachu's Electro Ball and his Stone Edge. Krokorok decides to help Ash and the group to find Pikachu which he had sensed where he is and they found Pikachu which Ash knows his moves where he was found by Mick. Krokorok allows Ash to use him to help Mick learn the techniques associated with battling. However, during that training, Pikachu manages to knock Krokorok with Iron Tail causing his sunglasses flying away which he put his sunglasses back on which Ash explains to Mick about Krokorok's scare when he loses his glasses. Krokorok soon attacks Pikachu from its attack but Ash stops him in time to replace Tepig in his place.Krokorok later teamed up with Pikachu under Mick's command in a Double Battle against a Seismitoad and Scolipede belonging to the father of a young boy, Sean. Krokorok and Pikachu eventually won. After the youngsters reconcile on their friendship, Krokorok attacks Pikachu with his Bite with the intention of settling their rivalry once and for all. Krokorok and Pikachu are equally match by using both Crunch and Quick Attack but Krokorok unleashes his Stone Edge to trap Pikachu on the ground and try to ambush Pikachu by Dig. Pikachu uses Thunderbolt on the ground to make Krokorok tripped, allowing Pikachu to knock his sunglasses with Quick Attack but he manages to put his sunglasses back on. Krokorok attempts to hit Pikachu with Crunch, but he was soon defeated by Pikachu's Iron Tail knocking him out. After a fiercely-fought battle, Krokorok was greatly depressed by the loss. Krokorok then attempted to leave but Ash then offered Krokorok the chance to join his team with Krokorok happily accepting with Ash catching Krokorok in a Poké Ball seconds later.
In An Amazing Aerial Battle!, with Krokorok now a permanent member of Ash's team, Krokorok was used in Ash's Gym battle against Skyla.Krookodile battled against Skyla and her Swoobat and was defeated with Air Cutter. He and Ash did some training with Brycen and his Beartic. It was used in the Icirrus City Gym where he was used against Brycen's Vanillish but was quickly recalled. He was later used against Brycen's Beartic which he won, winning Ash the Freeze Badge. Since he was fully evolved, he became a real powerhouse in Ash's team.
In Ash, Iris, and Trip: Then There Were Three!, Krokorok faces off against Iris' Dragonite in the Junior Cup which both Ash and Iris battle in whoever wins to face Trip. Krokorok attacks Dragonite with both Crunch followed by Stone Edge but it dodges both of his attacks and soon countered with Flamethower knocking him out as he stand up to fight. Krokorok dodges Dragonite's Ice Beam using Dig but its attack was still dodged allowing Dragonite to attack him with Flamethrower which he surprisingly dodges. Krokorok was soon attacked by Dragonite's Flamethrower but it didn't do a thing but it soon dodges it's Flamethrower using Dig and he counterattacked by biting on his tail using Crush making it to shake it off the ground and hit with its Ice Beam which he soon dodges it and attacks it with Stone Edge. Krokorok was soon mauled from Dragonite's Flamethrower followed by trapping with its Ice Beam then being knocked down by another Flamethrower. Krokorok manages to withstand the damage while struggling to get up as his eyes glowed in red while furiously yelled in rage to evolved into a Krookodile much to Iris and Dragonite's surprise and Ash's excitement. Krookodile manage to knock Dragonite with a newly learned Dragon Claw. Due to the damage is super effective, Dragonite goes out of control using all of his abilities and also disobeys Iris allowing Ash to win the match by biting Dragonite's hand using Crunch and defeats it with Stone Edge to knock him down.
In Meloetta and the Undersea Temple!, Krookodile is used in a special training with Meloetta in her change form until it was interrupted by Ridley and his Golurk came to find Meloetta for the long time.
In Team Plasma and The Awakening Ceremony, Krookodile teams up with Charizard to dig up the hole using both Dig and Dragon Tail combination to get Ash and N out especially the Light Stone they carried. They fought against Team Plasma grunts until Ash called them back to their Poké Balls when Doctor Colress turn on them to hit with his machine.
- He was set to appear in Team Rocket vs. Team Plasma! (Part 1) but the episode, along with Team Rocket vs. Team Plasma! (Part 2), was postponed and eventually cancelled.
- Krookodile is currently Ash's only Dark-type Pokémon to have used/learned any Dark-type moves.
- Prior to capture, Krookodile inherited the blast off gag from Team Rocket.
- Krookodile, like other recurring Pokémon, has an item it carries around, its sunglasses, but was the first to have been caught by Ash.
- Krookodile is universally considered to be among Ash's strongest Pokémon, along with Pikachu, Sceptile, Infernape, Charizard, and Greninja.
- Krookodile is the third Pokémon that Ash caught who had an accessory, the first being Squirtle (they both have Sunglasses) and the second being Sceptile (who had a twig).
- When the sunglasses that Krookodile wears are knocked off, it seems to always have a nervous breakdown, suggesting it may be a comfort object.
- Krookodile, like Ash's Primeape, evolved before it was caught.
- Krookodile's sunglasses grew in size when he evolved.
- Ash's Krookodile is the second Pokémon Ash has owned that he still now owns that has a unique type. His first being Torterra and the third being Hawlucha.
At Oak's Lab
At Kukui's house