Prior to being caught by James, Mareanie formed a crush on a differently colored Mareanie after he saved her from a Tentacruel. Later on, though, Mareanie spotted her crush giving a Corsola's horn to another Mareanie, leaving her heartbroken.
Mareanie first appeared in The Sun, the Scare, the Secret Lair!, in which she encountered James when he was wearing a scuba diving helmet resembling a Corsola. She latched onto his helmet, mistaking it for a real Corsola, causing it to crack and flood with water. After James reunited with Team Rocket, Mareanie latched onto his head and injected him with poison which caused him to resemble a Mareanie, causing Mareanie to become smitten with James. Later, during a battle with Ash, Mareanie jumped in to help Team Rocket and launched a Spike Cannon towards Pikachu. With Mareanie's help, Team Rocket gained the upperhand against Ash, poisoning his Rowlet and dealing serious damage to Pikachu. As Jessie's Mimikyu was about to launch one final attack, Bewear suddenly appeared from the water and took Team Rocket away with it. After being dropped off at Bewear's den, James asked Mareanie to join his team, which she accepted. After catching her, James called her back out, and Mareanie affectionately latched onto his head, making him look like a Mareanie once more.
In A Team-on-Team Tussle!, Mareanie assisted Team Rocket in their quest to obtain a Darkinium Z. She battled a TotemAlolanRaticate, which protected the Z-Crystal. Mareanie attacked with Spike Cannon, agitating it to follow them away from the Darkinium Z. She was then quickly defeated by Raticate's powerful attacks.
In Fighting Back the Tears!, Mareanie was reunited with her former crush, which evolved into Toxapex and fought James for her affections. She later ran away from Team Rocket after she overheard James talking about leaving her with Toxapex, and found sanctuary with Ash at Professor Kukui's house. The next morning, while walking along the beach, she was attacked by another Tentacruel, but she was saved by James. Despite their reunion, James still insisted on releasing Mareanie, leaving her in tears. However, James was then challenged to a fight by Toxapex to make Mareanie happy, which ended in a tie. Following the fight, Mareanie decided to stay with James, which he accepted.
Similar to a number of other Pokémon James has owned, such as Victreebel, Cacnea, Chimecho, and Carnivine, Mareanie is very fond of James and occasionally engulfs her Trainer's head in her ten spiked tentacles. The resulting poisoning causes James to look like a Mareanie. Mareanie has an attraction to James's appearance in this state, one of the reasons she decided to join him. In addition, Mareanie is shown to be a romantic, as seen in The Professors' New Adventure!, where she was drawn to the sound of Professor Kukui and Burnet's wedding, causing her to fantasize about marrying James, only to be snapped out of her delusion by her Trainer calling out to her. However, prior to the moment when she first poisoned James, she was shown to be quite grumpy, as shown when she slapped Jessie's hand away when Jessie first stroked her.
When James attempted to capture a female Frillish in Fighting Back the Tears!, Mareanie saw her as a rival for his affections and scared her away with Spike Cannon to prevent this capture. She then cried when James scolded her for doing so. She was shown to be very loyal to her Trainer in Why Not Give Me a Z-Ring Sometime?, where she used the newly learned move Knock Off to attack Jessie when the latter tried to steal James's creme puff.
Description: Mareanie's Trainer strikes a series of poses to build Z-Power. Mareanie then leaps into the air and a spiraling sphere of purple, red, and black energy forms above its head. Mareanie then throws the sphere at the opponent, and it expands into a miniature black hole. The opponent is sucked into the black hole, causing it to explode.
In the TCG
James's Mareanie is featured in the TCG as of one James's Pokémon. The following is a list of cards featuring Mareanie.
Mareanie Cards listed with a blue background are only legal to use in the current Expanded format. Cards listed with a silver background are legal to use in both the current Standard and Expanded formats.