Andrew Neiderman's book Pin was adapted into a film in 1988. It was directed by Sandor Stern.
The movie featured a plot rather faithful to most of the novel but with some changes. Leon and Ursula Linden are brother and sister who aren't quite your normal kind of people. They also love chatting with their friend Pin. Pin just happens to be their father's medical dummy. When their parents die, Leon decides to let Pin come and live with them at home. Clearly everything is just as right as rain in this house.
- Abusive Parents: Leon and Urusla's parents aren't still the best parents around.
- Adaptational Modesty: Ursula stays fully dressed when she destroys Pin. In the book she was topless. In addition to that a lot of scenes from the book with more open nudity are changed or elimiated.
- Adaptational Name Change: Here the family's last name is Linden, it's never mentioned what it is in the book.
- Barbie Doll Anatomy: Averted fully with Pin who is anatomically correct and is able to be used as a sex toy.
- The Beautiful Elite: Played with, while by the standards of their house and wealth Leon and Ursula put them upper class, they are very twisted.
- Becoming the Mask: After Leon witnessing Ursula destroy Pin, he collapses on the floor unable to move by himself essentially becoming the new Pin.
- Death by Adaptation: Aunt Dorothy dies after being scared by Pin, while her book counterpart is barely in the story much at all.
- Disposing of a Body: After Leon tries to kill Stan, he drags his body out and hides it under the wood pile.
- Don't Split Us Up: Leon and Ursula don't wish to be split up when their parents die. After the death of Aunt Dorothy they are old enough to avoid this.
- Frameup: Leon tries to confess that the whole thing is Pin's fault and that Pin killed Stan. Ursula doesn't buy it at all and goes to grab an axe.
- Gold Digger: Leon worries Stan is this.
- Incest Subtext: Unlike in the book, here it's only implied as Leon is jealous of Ursula's sexual habits.
- Neat Freak: Leon and Ursula's mother is one to the point she keeps plastic sheets over everything. When she dies, Leon and Ursula joke that she'll be asking God to take his shoes off.
- Old, Dark House: The house Leon and Ursula live in is one.
- Parental Favoritism: Their father tends to give Ursula the easier questions during his quiz rounds putting her ahead of Leon who is given much harder ones.
- Really Gets Around: Ursula at least at first to the point local school graffiti includes "If you want an easy screw, Ursula will do". As she grows up this is an averted trope.
- The Reveal: The reveal that the dummy the kids are scared of at the beginning isn't Pin but instead Leon after he has become like Pin
- Sanity Slippage: Leon slowly loses his mind as the movie goes on.
- Leon starts to think Pin is alive and uses ventriloquism to act as if he is talking to other people. Somewhat of a Split Personality and somewhat an Imaginary Friend. When he overhere's Stan talking behind his back about being unstable Leon eventually tries to kill him. Once Ursula realizes this she grabs an axe and destroys Pin. Leon witnessing this breaks down leaving only the Pin personality in his body to sit there acting like a dummy.
- Shout-Out: Pin is short for Pinocchio
- Spared By Adaptation: Stan survives in the film where he dies in the book.
- Troubling Unchildlike Behavior: Due to how they are raised, Leon and Ursula have sex rather early and at generally show this only gets worse as the story goes on.
- Ventriloquism: Leon and Ursula's father used Pin for this to help with patients and also give him someone to talk to. Leon learns it as a part of his Sanity Slippage. This is a departure from the book where it's all in his head.