Something looks off about those car pieces; you wander over and notice that they seem to have been modified in odd ways.
Picking up one of the heavy wheels, you notice that it has a hollow in the middle, with a space large enough to fit your hand in. A quick check shows that, with a little creativity, you could probably fit your limbs into most of these components.
You look around, checking no one can see you. It's dumb, but you feel like trying on some of these pieces. Unable to resist your curiosity, you pick up a discarded headlight. The wires have been twisted in such a way that you could hang it on your head like an eye-patch.
Gently, you rest the opening on the headlight on your eye, and fasten the wires around your head. You are quite surprised to find that you can see through the yellow plastic, though it is very dark.
Amused by how silly you must look, you put the other headlight on as well. Then you grab a couple of wing mirrors, and push your ears into gaps on the side, leaving them pointing from the sides of your head.
Looking in the shiny surface of the car's metal body, you can't help but laugh at your ridiculous appearance.
However, you find that you are really enjoying yourself. You want to see just how many of these components will fit on you; you have at least an hour until Jack finishes watching the television.
You root through the machinery and find a modified dashboard, twisted around and beaten into a vaguely torso-like shape. You pull off your shirt and slide it over your head, where the plastic rest gently on your chest; the dials are just on top of your nipples.
You also find a set of hydraulic brakes which slide slightly uncomfortably over your legs, and seatbelt fasteners which clip onto your shoulders, the belts wrapped tight around your arms.
Under a large piece of metal, you find some very curious pieces.
First, a miniature grille, bent into a smile-shape. You turn it around, and try pushing it into your mouth. It twists your lips painfully, but it just barely fits.
Looking at yourself in the mirror, you laugh, and your tongue catches on something soft on the back of the grille. You jump as it makes a blaring car-horn noise.
Fortunately, no-one seems to have noticed. You try again; it seems that you can make a horn noise by biting the rubbery ball on the back of the grille.
However, your eyes are drawn to the last remaining pieces; a weird, jockstrap shaped plastic can, and a gear stick.
First, you take the can. It is a rigid piece of translucent plastic shaped like the front half of a jockstrap, with a hole in the front.
Eventually, your curiosity gets the better of you, and you remove your pants and underwear, before sliding your hard dick into the hole. The can fits perfectly, clipping snugly over your balls and around your hips. As you move, the thick black oil in the bottom of the hollow can sloshes about.
You pick up the gear stick. It is hollow, and your attention moves automatically to your dick. You can't help yourself as you slide your dick into the stick, the insides smooth and slippery.
To your surprise and pleasure, stroking the hard plastic feels like stroking your own dick! Unable to resist, having gotten hard from your weird activities, you begin pumping the hard plastic, hardening and exciting your dick. You don't notice as the oil in the can bubbles and sloshes, and soon you bring yourself to orgasm, biting hard on the horn and producing a blaring honk. Something thick and sticky seems to flow into your balls, inside you and up out through the gear stick, and you open your eyes to see hot, sticky black oil spurt out onto your chest and into a puddle on the floor.
You slip on the oil, and your foot accidentally hits a wheel, sliding into the gap. The wheel is standing perpendicular to your foot, and when you try to pull it out, it spins, causing you to thrash about, trying to stop yourself falling, only for your other foot to slide into another wheel!
Unable to balance on two wheels, you fall forward, both of your hands moving down to catch yourself, and sliding firmly into two wheels stacked side-by side.
You struggle into some sort of upright position. You are on all fours, both hands and feet stuck in large wheels, with headlights, wing mirrors and a grille on your face, a dashboard on your chest, seat-belts and brakes on your arms and legs, a can of oil on your balls, and a gear stick on your cock.
If someone catches you like this, you'll die of embarrassment.
You look around, trying to see something to help you get out of this predicament. There is a large, oily engine on a couple of bricks just behind you, and large sheets of metal for a car's chassis, but nothing looks to be of use. Your arms and legs are stuck in this splayed-out position by the wheels, too. You try rolling forward and back-wards, trying to get some momentum, and hear the noise of some bricks falling as your rear wheel hits something.
You honk in pain as something rigid and cold rams into your ass. You pull your head around, with a lot of difficulty, to see that a large pipe on the engine has gotten stuck up your ass. You start struggling, but the pipe only slides in deeper. In fact, it's like the engine is unraveling to slide into you. You pull back roughly, and feel the huge, hard metal force your ass open, and slide inside.
You honk painfully as you feel the metal pierce your insides, the cold pipes jutting into your organs and wrapping around inside you.
You feel awful, barely able to move and with an aching ass. Your skin feels cold and hard; you are freezing, but don't seem to shiver. There is a click and a whirr, and the area in front of you is illuminated by a yellow light. Somehow, the headlights have come on.
You feel a terrible urge to sneeze, which builds and builds, before falling away. This happens again and again, with a loud mechanical whirr each time, until you suddenly let loose, with a loud roar of a running engine. Your wheels spin suddenly, crashing you into the piles of metal, and you fall onto a large sheet of steel. The steel pushes against your cock and balls, and you feel them seem to push deeper inside you. you struggle, causing another piece to topple on top of you, slamming into the one under you with a loud click.
You look around, and see the shiny metal in front of you. The piece under you is the underside of a chassis, cold gunmetal gray, and twisted with mechanical components. It has slid neatly around the wheels, hiding your legs completely. The piece on top of you is a rusty blue top half of a car; it has fallen snug around your face, covering the areas of skin but with holes for the headlights and chassis.
You are contemplating how odd this looks, and how strangely shaped the chassis is, when you hear the garden door open. Jack walks over, scratching himself, and you try to speak, to explain your ridiculous predicament, but can't seem to form any words.
Jack roots around in his pocket, and pulls out a greasy set of keys. He slides them into a lock in the car door; you are shocked to find you can feel it happen! He pulls open the door - YOUR door, and slides in. You rest down on your wheels under his heavy bulk. You can feel his ass pushing against your tattered seats, and his sweaty back resting against your own.
He pulls down a seatbelt, and fastens it, and you feel as though you are hugging him with thin, weak arms. He pushes his key into the ignition, a feeling which thrills you, and begins turning. At the same time, he pulls and shifts the gear stick, and you feel it as though he is playing with your cock.
You are getting dizzy with pleasure. As he shifts your gear-stick-cock and turns your engine, you get hotter and hornier, your mind getting foggy. Your face stretches, the grille pushing into a real metal car-front, as your ears migrate up next to the driver windows. your arms and legs shift, conforming to their proper places in the chassis, and your balls recede to the gas tank. You feel your consciousness spread to cover the entire old, rusty car, and somehow you can feel your memories and knowledge clustering together in what feels like your ass.
Finally, with one rough turn, your engine starts, and you orgasm, pleasure running through your body literally like electricity. You roar with life, and your old personality fires out of your exhaust pipe as a thick, choking cloud. All that you were is gone, now, and you are just Jack's old, rusty car, ready to drive.