When Mareanie sees James' purple face after he gets poisoned by her, she has a strong affection on him, even blushing red. Also, she likes to grab his head using its tentacles.
She is very jealous of other Pokémon, whom she think one of them are females and trying win over James’ heart, causing James’ Pokemon capturing messed up. She was originally in love with a male Mareanie (later evolved as Toxapex in the present), until she thinks he dumped her for another female Mareanie, displaying her hatred toward her ex-boyfriend.
Sometimes in the past, the Mareanie was attacked by a Tentacruel, until a male Mareanie, whose is much older than saved her life as she fell in love with him. Unfortunately, Mareanie’s love for the male Mareanie did not last long, thinking that he dumped her for another female Mareanie. Heartbroken, Mareanie would never love the male Mareanie ever again.Mareanie first appeared attacking James because she wanted to eat his Corsola-shaped helmet, but later felt disappointed when she found out that it was only a helmet. After Jessie, who was attacked by her tentacles, gave James a push, she poisoned him, causing him to look like another kind of her species. Thus she blushed and started to chase him, much to his dismay. However, she later helped Team Rocket and she was so strong that she managed to poison Ash's Rowlet. However, Mareanie was taken by Bewear along with Team Rocket. After arriving in Bewear's home, Mareanie was formally asked by James if she wanted to join him which she accepted then was caught.
By the time she was encountered again by the male Mareanie, she keeps rejecting his advances. Upon seeing her affection towards her Trainer James, the male Mareanie attacks him with Spike Cannon as it suddenly evolves into a male Toxapex and manages to poison him. Mareanie scolds him for what he had done causing it to run away.
Mareanie became depressed when her Trainer is poisoned by a male Toxapex and decides to leave Bewear's den and briefly stays at Professor Kukui's house where he, Ash and his wife lived. Mareanie remembers the good times with James and finally decided to get back. As she is about to get back, she was soon attacked by a wild Tentacruel but James rescues her. She later watched her Trainer battles with Toxapex and Jessie, Meowth and Wobbuffet and became impressed to see their battle is a draw. She thanked her Trainer for protecting her and Toxapex from a wild Tentacruel, and Toxapex gives him the Corsola horn due to his affection with Mareanie causing James to run away while being chased by both Mareanie and Toxapex.
During Team Rocket's trip to Ula'ula Island, Mareanie learned the move, Knock Off to defend Acerola from a Gengar named Greedy Lapoo. She then performed the Z-Move, Black Hole Eclipse to finish Gengar off.
At the Alola League, Mareanie was used to battle against Wobbuffet and won, which allow James to move onto the Quarter-Finals. It was later used in a battle against Gladion's Lycanroc. Mareanie attempted to used Black Hole Eclipse to defeat Lycanroc, but Gladion countered it with Continental Crush and defeated Mareanie with a close range Stone Edge.
Soon after the Alola League, Team Rocket received a call from Giovanni and were ordered to return to Kanto due to their lack of achievements in Alola. Jessie and James, knowing that Mimikyu and Mareanie would be unhappy in Kanto, decide its best to leave them behind. However, when James tried to explain to Mareanie about their departure, Mareanie believed that she's coming along as well and got super excited. As Mimikyu and Mareanie slept, James entrusted Mareanie to take care of their Z-Power Ring and Z-Crystals. Team Rocket then left Alola and returned to Kanto. The next day, Mareanie is last seen playing with Mimikyu and Stufful.
- Like Victreebel, Cacnea, Carnivine and Chimecho, Mareanie is the fourth Pokémon that shows affections for James.
- Mareanie is the first Water-type Pokémon that James officially keeps on his team.
- Mareanie is the second Pokémon James has owned that shows affection to him and is not a Grass-type. The first one being Chimecho which is a Psychic-type.
|Team Rocket's Pokémon|
|Jessie · James|