A kid who has to constantly 'perform' in school, extra-curricular activities, etc., just to keep their parents off their backs. These same kids are also expected to just take it (it being everything they go through), instead of venting their frustration or weariness aloud and be seen as a whiner or emotional lazy brat. A wind-up doll's parents often claim to push their kids into activities to help their grades/improve chances of getting into a good college, but are reluctant to let the poor tyke relax before he/she snaps a la Mariah Carey. Wind-up dolls either run away, go insane and take out a few people with them, or just ice themselves. (Anything to escape having to be Mommy's or Daddy's little circus clown, huh?)
Most soccer moms' children are, in fact wind-up dolls.