Litten is a kind of Pokémon that tends to keep its emotions to itself. It had a very close friendship with its mentor and guardian, Stoutland, who took care of Litten after it was injured. Its friendship with Stoutland caused Litten to have dreams about Stoutland leaving it without warning.
Since its debut, Litten had difficulty getting along with humans, but seems to get along with the old lady at the marketplace. When it first met Ash, Litten didn't have complete trust in him and refused to bond with him. However, when Stoutland was ill, it shook away its distrust towards him and it was desperate to come to him and ask him for help. After Litten accepted Stoutland's departure and joined Ash's team, Ash had finally earned Litten's trust. Litten appears to have grown to like and respect Ash.
After being caught, despite it prefers being alone most of the time, Litten starts to warm up with the others around it like showing affection and encouraging Ash. Litten grown to be very protective towards its friends shown when a wild Palossand was about to swallow Rockruff it kicked it’s friend away to save it. Litten even became good friends with Snowy (Lillie's Alola Vulpix) when it stayed with Ash temporarily.
On the other hand, Litten doesn't like being hugged affectionately, as shown when Delia hugged it when she saw it, causing it to feel uncomfortable. However, when Delia gently stroked Litten on the chin, it couldn't resist it.
Similar to Ash's Charizard, Litten seems to have a habit of spitting fireballs onto Ash's face.
Litten is very clever as well since it was able to give a touching speech to Team Rocket in order to cause them to lose their guard before defeating them.
Litten has a little bit of a rivalry with Lycanroc to see who's stronger or to show off also they would have contests.
Litten first appeared where it went to lie down at a beach and licked its paw. But Ash and Pikachu, who were running fast and causing a sand burst pass by it with Ash stepping on Litten's tail and got covered in sand. Ash attempted to apologize, but the angered Litten used Ember, burning his face and causing him to faint before it walked away. Litten went to the Pokémon School, where it saw a Komala sleeping in a tree. Litten reappeared again where an elderly woman was kind enough to give it food before noticing a flock of Pikipek and a Rowlet come to take some food that the people were offering.
When Ash met Litten, the latter showed his friendliness towards it by giving it a small piece of sandwich, but it took the rest of the sandwich instead and scratched Ash's face, who tried to get it back when he pulled its tail and even kicked Rotom Pokédex. Unfortunately, an Alolan Persian took the sandwich away and even made the sandwich turn into ashes by throwing it when Litten used Ember. After a while, it stole a piece of Team Rocket's fruit and attacked Meowth, who tried to use Fury Swipes, and caused the rest of Team Rocket to get burnt as well. When Ash saw it again, he chased it and was shocked to see the old lady offering it an Oran Berry. Later, it was revealed that Litten lives in an abandoned building along with an elderly Stoutland, which was its adoptive parent. As Stoutland was too old and couldn't move around much anymore, Litten had to bring it food. The next day, Ash, Pikachu and Rotom witnessed it trying to keep its Sitrus Berry from the Persian and they saved it from the Persian. Despite it rejecting Ash's friendliness, it was shown that it got hurt and so, Ash took it to the Pokémon Center. During this, it met Ash again at night and battled the Alolan Persian that attempted to steal its food and they won. As Ash and Pikachu arrived with food, Litten and Stoutland were gone. Ash returned to the Market when Litten appeared. Afterwards, it became nicer to Ash at the end of the episode by accepting the mangosteen he offered as it departed off.
It appeared again when Team Rocket tried to catch Rowlet and Popplio and takes them to see Stoutland in their new home. Then, the Big-Hearted Pokémon told Litten to escort the duo back to Ash and Lana; along the way, they get caught in Team Rocket's trap but the Fire Cat convinced the trio that it wanted to join them. But all it did was cut the net and Team Rocket was sent blasting off. With Rowlet and Popplio safely returned, Litten jumped across the rooftops of the city into the distance.
Litten was seen stealing a doughnut from Ash when the old lady was about to hand the doughnut back to Ash and it gave the food to Stoutland. It tried to learn Fire Fang from Stoutland but failed, although Stoutland had done its best to demonstrate the move. Litten began to worry about Stoutland, who was growing weaker than before, and it had to ask for help from Ash as Stoutland fell unconscious. Nevertheless, due to the distrust for humans, Litten decided to take Stoutland back home. In its dream, it saw Stoutland was fading away further and further until Stoutland vanished. The next morning, it searched for Stoutland at different places, including the abandoned house and the cliff, but when it went home, it eventually understood that Stoutland was dead as it noticed the leg of the couch broke and the withered tree losing its last leaf. After Stoutland passed away and felt like it has nowhere to go, it saw the rainbow in the sky and the soul of Stoutland among the clouds. Then Ash offered Litten to come with him and it had a battle with Pikachu. Though the battle ended in a draw, Litten was thankful to Ash and finally trusted him, hence joining his team.
Soon, Litten was training with Kiawe and his Turtonator so that it can fully master Fire Fang. But it ended up in unsuccessful attempts when Litten tripped over an empty soda can. The training session was interrupted when Ash got swallowed up by an angry Palossand after he planted Rotom on its head, thinking it would replace its lost shovel. Rockruff tried to fight Palossand, but Litten protected it and ended up getting swallowed as well. Then, Palossand began to absorb Litten's energy, making it unable to exit Palossand's body. However, thanks to the combined efforts of Ash's classmates, Lillie's Alolan Vulpix froze the angry Palossand with Powder Snow and stopped it from absorbing Litten's energy. Litten manages to fully master Fire Fang and used it to break itself and Ash out of Palossand's body. After that, Ash and Litten returned the lost shovel to Palossand and the Sand Castle Pokémon was finally calmed down.
When Delia Ketchum arrived in Alola for Visiting Day, Litten freaked out and got very embarrassed at her sudden approach. However, once Delia started petting it, it got more comfortable with her. When Tupp, Zipp, and Rapp started attacking the school and planned on stealing the Poké Ride's Tauros, Delia ordered Litten to attack despite its embarrassment towards her. Later, it was briefly used when Ash sent it out along with his Rockruff and Rowlet to find a Charjabug and give it to Sophocles for a present. It was seen aggressively play fighting with Rockruff before its battle with Gladion where both stayed off at a stalemate. Litten attended the Wela Volcano Park crowning ceremony but the crown got snatched by a wild Alolan Marowak when it was Litten's turn. When Kiawe and Ash were battling that night, Litten was seen sleeping. The next day, Litten got crowned and it was included in the class pictures. Litten was called in to battle the Totem Lurantis at the end of Ash's Lush Jungle Trial. Litten had the edge with its fire type moves, but when Lurantis calls for its ally Castform and uses Sunny Day. The battle becomes a struggle for Litten as it's two against one but thanks to Rowlet the battle was even. They were able to take out Castform and Litten finished out off Totem Lurantis with Breakneck Blitz earning Ash the Grassium Z Crystal.
During Ash's Grand Trial against Olivia, Ash told Litten and Pikachu to offer him support during the match. When Rockruff suddenly bit Rowlet, Litten and the others were astonished.  Litten, along with Rowlet, was alerted that Ash was missing, but so relieved that he and Pikachu were alright. Once the pair was okay, the returned to Ash who informed them that Rockruff was missing and they had been searching for their friend. When they found it, Litten witnessed Ash, Rockruff and the two Lycanroc being healed by Tapu Lele. They also saw Rockruff evolve into a Dusk Lycanroc, and Litten expressed its delight to its canine friend upon evolving by rubbing itself on Lycanroc's body. Soon, Litten and the others went back to Melemele Island after the kids' special classes on Akala Island had ended.
Litten is always carried by Delia during the reunion party at Professor Oak's lab 
Litten attended the lecture in the Cerulean City Gym, where it witnessed the strength of Brock's Steelix and watched Ash's Pikachu fight Misty's Gyarados. As Ash was going to be late for school but he refused to wake up, Litten obeyed Rotom's order and slapped Ash and Pikachu on their faces by using its tail, making their cheeks swollen. As Litten was scared by Ash's poorly-made bubbles, it tried to run away but accidentally made Lycanroc dirty. Then, when Lycanroc and Litten started to fight, Ash, who interrupted their fight, got his head bumped. It battled Dusk Lycanroc while Ash was away after the class's sleepover and was winning the match using a Fire Fang, but the result wasn't shown.
Litten later teams up with Rowlet in defending Mallow, Sophocles, Lana and their Pokémon against Lusamine's Pokémon under her control when she was fused by Nihilego.  Litten is able to defeat Lusamine's Lilligant with Fire Fang before it unleashes its Solar Beam until it awakens to confront them again due to Lusamine's control.
|Ember +||Alola to New Adventure!|
|Fury Swipes||That's Why the Litten is a Scamp!|
|Slash -||They Might Not Be Giants!|
|Fire Fang +||One Journey Ends, Another Begins...|
|Scratch +||Alolan Open House!|
|+ indicates this Pokémon used this move recently.*|
- indicates this Pokémon normally can't use this move.
|Breakneck Blitz||Currying Favor and Flavor!|
|+ indicates this Pokémon used this move recently.*|
- indicates this Pokémon normally can't use this move.
- Litten is another Fire-type starter Pokémon that Ash caught that was not to have an abusive trainer previously, which is another occurrence of the case in Alola as with Quilava in Johto.
- Litten is also the first Fire-type starter Pokémon not to have any experiences to defend itself from the abusive trainers.
- Delia and the old lady both like to refer to Litten as "Littie".
- ^ SM001: Alola to New Adventure!
- ^ SM003: Loading the Dex!
- ^ SM004: First Catch in Alola, Ketchum-Style!
- ^ SM007: That's Why the Litten is a Scamp!
- ^ SM016: They Might Not Be Giants!
- ^ SM021: One Journey Ends, Another Begins...
- ^ SM022: A Shivering Shovel Search!
- ^ SM024: Alolan Open House!
- ^ SM026: So Long, Sophocles!
- ^ SM027: A Glaring Rivalry!
- ^ SM034: A Crowning Moment of Truth!
- ^ SM035: Currying Favor and Flavor!
- ^ SM036: Trials and Determinations!
- ^ SM037: Rising from the Ruins!
- ^ SM042: Alola, Kanto!
- ^ SM043: When Regions Collide!
- ^ SM044
- ^ SM047
- ^ SM049
- ^ SM053
- ^ SM054