Inkay appears to be a sneaky and mischievous Pokémon, as he was seen stealing food from Team Rocket and then followed them in their balloon. He seems to love food (especially crossiants) and would often go out of his way to steal it. However, James at one point used this to his advantage to capture Inkay.
Despite being very mischievous and being a Pokémon owned by Team Rocket, he possesses their recurring trait of being very loyal to his trainer and comrades. His relationship with James has often proved affectionate. Inkay holds a deep grudge against the evil Malamar he encountered during his travels, namely for brainwashing James, and would do anything to stop it from fulfilling its dark plans of destroying the world.
Though often on the losing end like the rest of its team, Inkay has often proved a challenging opponent, having injured and matched key battlers such as Ash's Pikachu or other Pokémon on several occasions.
Inkay first appeared while Team Rocket was dining at a café in Lumiose City. As Team Rocket were busy celebrating news from Giovanni, Inkay stole their food and proceeded to eat it from under their table. While Team Rocket were on their balloon, the same Inkay from before approached them when they dropped their sandwich and sprayed ink at them. After Team Rocket cleaned themselves off, James scanned the Inkay to get some details about him and the Team Rocket trio attempted to battle it with Wobbuffet. However, James offered Inkay some food instead as bait. While Inkay was distracted, James threw a Poké Ball and caught him, much to the surprise of Jessie and Meowth.
Quickly becoming beloved by James, Inkay would prove to be a formidable battler afterwards, antagonising Ash's team effectively several times and even overpowering the forces of Officer Jenny. Nevertheless he could not break the team's losing streak against the twerps. Inkay was also used to impersonate Ash's Pikachu in an attempt to cause havoc in a town in Heroes - Friends and Faux Alike!.
Since A Conspiracy to Conquer!, Inkay formed a grudge against the evil Malamar who used Hypnosis on him as well as his trainer, Jessie, Pumpkaboo, Ash's friends, Pikachu, Officer Jenny, Wobbuffet, and several Pokémon for its own selfish desires of conquering the world. In Facing the Grand Design!, when everyone was kidnapped by the three evil Malamars except for Clemont, Meowth, and James, he convinced the good Malamar and several other Inkays to fight against the evil Malamars, stop their plans and save their friends from mortal danger. However, during the rescue mission, one of the evil Malamar brainwashed Inkay and forced him to attack everyone. But James managed to save Inkay by breaking him free from the evil Malamar's hypnotic control and Inkay continued the battle to save everyone. After the evil Malamar escaped into the future, James attempted to release him so he will live with the forest Pokémon near Grace Tower. However, Inkay refused to leave James since being with Team Rocket is what makes him more happier. James cried tears of joy and promises to catch Pikachu together.