Clarissa's Arcanine

Clarissa's Acanine is a Pokemon she obtained in Kanto.

As a Wild Pokémon
Arcanine as a Growlithe was found on Kanto Route 8 with Vulpix. The two were being hunted by Pokénappers and Growlithe defeated them with the aid of Clarissa's Charmander and Jolteon. Clarissa asked him and Vulpix if they would like to join her on her journey. Vulpix accepted and Growlithe accepted if he could battle her first. Growlithe ended up tying with her Haunter.

With Clarissa
Growlithe was very distant at first and only would interact with Vulpix until Haunter helped him open up to the rest of the team. Eventually Growlithe decided to evolve into Arcanine after a devestating loss against Regina's Nidoking. Arcanine became much friendlier over time and was used in Clarissa's battle against Noland.

Personality
Arcanine is shown to be distant towards any Pokémon other than Vulpix and has a strong distrust towards humans. It took awhile for Clarissa to befriend her own Pokemon but the two formed a strong bond. Arcanine also is good friends with Clarissa's Gengar, who was the first Pokémon other than Vulpix that was befriended by him.