Scary Monsters Super Creeps
Warning: Do not look at the following link while sitting at home alone at night. You have been warned. By this warning.Okay, go ahead and look. But come back afterward to share the fear.
Welcome back. Yeah, that was my reaction, too.
I think having a doll custom-made to look like your kid could be the subject of an entire library full of horror novels, so I won't even go there. Here are some plots for novels of other genres:
Mystery/Thriller: A My Twinn(registered trademark) doll goes to the Doll Hospital for a makeover and winds up "broken." Her wise-cracking private investigator/bounty hunter Human Counterpart infiltrates the hospital, only to discover that the doll-killer's real target is...herself.
Literary: Protagonist, who left his tight-knit family to move to the opposite coast and become a writer, comes home to help his resentful sister take care of their dying mother. He discovers that his My Twinn(R) doll has replaced him in his mother's favor because "he's always there" for her.
Romance: Spunky divorce attorney Clarissa Lamont has met her match: the Machievellian Trent Montgomery will fight to the death for his client's right to keep custody over her children and their corresponding My Twinn(R) dolls. Will Clarissa fall prey to Trent's wiles, or will her own client (played by a winsome Jeff Bridges) steal her heart with his deep emotions and charming though infantile fixations?
Submit your own My Twinn(R) plotline! I'll give a $5 gift certificate for the online bookstore of your choice to the winners in the following categories: 1) Funniest 2) Most Believable and 3) Most Likely to Keep Me Sleeping With the Lights On for Three Weeks Straight.

