From Bulbapedia, the community-driven Pokémon encyclopedia.
Charla (Japanese: リサ Lisa) is a Charizard who lives in the Charicific Valley. She is voiced by 愛河里花子 Rikako Aikawa in both Japanese and English.
Charla belongs to Liza, who maintains the Valley. When Ash and his friends were going through the Valley, they had the opportunity to meet Charla. When Ash sent out his own Charizard, he began to show off in an attempt to impress her, indicating that he had fallen for her.
That love became more apparent when Ash's Charizard eventually tried to impress Charla by climbing to the top of a mountain, even after falling into a pool of water. Charla eventually accepted Ash's Charizard, returning his love.
Trivia
Her Japanese name, リサ Lisa, comes from Charizard's Japanese name, リザードン Lizardon, and is also a girl's name. Likewise, her English name comes from a portmanteau of Carla, a girl's name, with Char, part of the name of all of the members of the Charmander evolution family.
Related articles
For more information on this Pokémon's species, see Charizard.