Charlés is a talking cat with the same type of magic as Happy.
Her personality is strict and straight. She disapproves of fooling around.
Towards Happy she is very cold at the beginning but starts to soften over time. Especially during the Edolas arc has their relationship improved.
Charlés is actually a magical creature, called Exceed, that comes from the world Edolas. The official reason for the Baby-Exceed to be sent to Earthland is to kill the Dragon Slayers. As it turns out, the real reason was to protect them from the destruction of Edolas and the Exceed-kingdom of Extalia. It is also later discovered that she is the Exceed’s princess, daughter of Queen Shagotte and as such she possesses the same power as her mother: prevision. Due to that, she always knew of the pretense mission of the Exceed in Earthland and believed it to be her actual mission; to kill Wendy. This causes her a lot of stress and psychological pain during the Edolas arc.