Fremont Daughter

This girl briefly became the unwilling vessel of the demon Lilith.

Season 3
When Lilith decides to take a vacation, she possesses this little girl and forces her family to do her bidding. While everyone complies, Lilith acts like an ordinary happy girl, but when she is angered, she kills someone, as she had done with the babysitter, the pet Freckles, and later, Pot.

Sam, Dean, Bobby and Ruby come to her neighborhood in hopes of killing Lilith and saving Dean from his crossroads deal. They manage to sneak into the house, and Sam finds the daughter asleep on her mother, who beckons Sam to "do it".

The girl wakes up and sees Sam holding a knife. She starts screaming, but before Sam can harm her, Dean stops him and tells him that Lilith had left.

After the girl and her mother are taken to the basement and hide with her father, the brothers soon find out that Lilith left the girl for Ruby's vessel.

Season 4
When Dean suffers from ghost sickness, he has an hallucination of Lilith in the form of the Fremont child. She taunts Dean and nearly kills him with a heart attack, until Dean manages to recover.

Appearances
Season 3 Season 4
 * No Rest for the Wicked
 * Yellow Fever  (as a hallucination)