On one of the shelves, you find a black leather collar with small metal rings to lock it, and a silver dog tag attached to it. You've always wanted to know what those things feel like, and since there's no one around, you put it around your neck and click it in place...to a human, collars are a bit uncomfortable but not undoable. Suddenly, a glowing rash sweeps across your body and you quickly take off your clothes to see what the problem is. Fine black and brown hairs are sprouting from your skin, quickly forming into a shiny black coat with brown across the front. Your fingers and toes melt together into small hard paws, your fifth digit reversing its position to the back of the paw. Black claws pop out of the tips, producing a soft tapping sound as they hit the wooden floor. Your legs are now just as long as your arms, strengthened with some extra muscle to support your almost completely quadrupedal position.
Your teeth grow long and sharp, your tongue broad and flat. Following your face pushing out into a short muzzle, your nose turns flat, black and leathery, and your ears become pointier and flop over a bit. You try to express your surprise at what's happening, but all you manage to produce from your thickened neck is loud barking. The frame of your body shifts around a lot, readjusting bones, changing your proportions and straightening your spine from which now a short stump tail comes forth. You look around at the stump above your butt and are able to wiggle it a bit, being one of the few ways you are still able to communicate. You have become a Rottweiler dog from tip to toe, and there's no way you're gonna be able to get this collar off...