I don’t know about other writers, but I often have to answer this question for myself, “What am I going to do with a character that just showed up in my head and I absolutely hate?”
The obvious answer would be, “Don’t use him or her.” But, the imagination has its own unwritten and unfathomable rules that it doesn’t like broken – and will keep reminding you of that fact again and again and again until you give in and do something with the character.
Case in point: In my murder mystery, Corpse Pose, there is a woman named Hannah Townes. She’s the hypochondriac from hell. Obnoxious, needy, with an obsession to describe her imaginary illnesses to everyone she meets, she wears you out within five minutes of meeting her.
When Hannah first appeared in my mind, I detested the woman and told her to go away. But, true to her nature, she refused to disappear. She just kept popping up and, just like the Whack-a-Mole game, every time I hit her on the head with a mallet, she’d pop up somewhere else.
I only take so much mental punishment so I gave in and incorporated Hannah into the story. There’s no doubt she’s an integral part of Corpse Pose, but – you know what? – I still detest her to this very day!