This Growlithe, nicknamed Growlie, is a Fire-Type Pokemon owned by James.
Growlie is extremely loyal to James from his childhood until he grows up as an adult. Growlie was shown tackling the door angrily because it wants to break out of its dog house in order to save its master but when Ash being assisted by Misty, Brock, Jessie and Meowth to unlock the door, it quickly rushes to save him. When James is about to leave the estate after he tells it to take care of his parents, Growlie sadly howls on its master's departure.
In the Treasure is All Mine!, Growlie reunites his master one last time after it blew his disguise and as a member of Team Rocket. After defeating the robotic treasure box, James convinces Ash to use his Pikachu to be blasted off so that to avoid his fiance Jessiebelle and Growlie watches its master being blasted off by Ash's Pikachu's Thunderbolt.
Growlie is actually the nickname of James' Growlithe. It debuted in Holy Matrimony. It later reappeared in The Treasure Is All Mine! which showed more of James' past and why his parents wanted him to marry Jessiebelle. It is still with James's parents, remaining loyal to them. It helped James to run away.