This Cacnea is a Grass-type Pokémon previously owned by James. It was the first Pokémon he caught in the Hoenn region. Eventually, James gave Cacnea to Gardenia for training.
Cacnea from its debut is shown to be happy and energetic. It's notable gag is similar to both Victreebel and Carnivine when showing its affection towards its trainer James by hugging him after releasing from its Poke Ball. In Once They Were Greenfields!, Cacnea is shown to be desperate and determined when using Needle Arm during practice while trying its best to learn Drain Punch but it was still a lack of practice.
Every time Cacnea came out of its Poké Ball to battle, it would latch onto James out of affection, which would hurt him with its spikes. It met him and is crew right before James released his Weezing, and it saved them from a group of Beedrill. Cacnea was still following them to open the box James had given to it. Not that long after Weezing's release, Cacnea joined James' Team.
In Sweet Baby James!, Cacnea is used to fight Jessie's Seviper, after James saw both Jessie and Meowth are stealing his grandparents Pokemon including Mime Jr. and May's Munchlax. Jessie calls James a turncoat or a traitor because of his actions as James replies that he did this for the sake of his grandparents. Jessie, Meowth and Seviper are eventually blasts off from Ash's Phanpy's Hidden Power and Cacnea's Pin Missile.
Later when Jessie and James were in Sinnoh after their travels throughout Hoenn and the Battle Frontier, James continues using Cacnea while teaming up with his childhood Pokemon, Carnivine.
In Grass-Type the Always Greener!, James uses this to fight against Ash along with his Carnivine. Therefore, Gardenia who is the Gym Leader of Eterna Gym appears to be extremely interested in both of James' Grass-Type Pokemon much to his disappointment even he gets mad at her not to touch them.
However in Once They Were Greenfields, James teams up with Gardenia after she was amazed on Cacnea's strength and abilities when knocking its opponents with its Needle Arm during tag battles especially their motives with Jessie and Meowth are also interuppted by this. Gardenia knows that Cacnea also has a Drain Punch move which James does not know it has this ability in the first place since he mostly use both Pin Missile and Needle Arm. Cacnea uses Drain Punch to knock Turtwig but after usage it loses its strength once it was used again. Gardenia convinces James that his Cacnea has to train its Drain Punch due to its lack of practice and wants to let her trained it before they ended up losing the match. James decides to let Cacnea practices to learn Drain Punch even Ash's efforts as well and Cacnea was desperate to learn its move. Because of its lack of practice and needs to master it, James decides to give Cacnea to Gardenia so that it will trained for its Drain Punch and he tells it that he is not good enough to train it as it allows it to put it back into his Poke Ball and gives it to Gardenia and he tells her to take care of Cacnea and Gardenia accepts and she can raise it well and James emotionally runs away while Jessie and Meowth followed him. Cacnea is last seen with Gardenia ready to train with her while James sadly watches his old Pokemon in Gardenia's care.