…no, wait, let's set this up first: you immediately transform into a greyhound taur, imagine a centaur, but instead of a horse lower body and a human upper body, both of them are canine."
Jen felt two new canine legs grow from her midsection until they touched the floor, while a tail sprouted from her rump and fur grew all over her body. Her mouth and nose extended into a muzzle, and her hind legs turned into digitigrade paws while her hands become paw-like, though with the fingers still separable. She stretched her arm backwards and ft her lower torso in the way. She rushed to the mirror on her four legs, and saw a quadruped greyhound body below her waist and an upright greyhound body and her head above.
"Now, every time you lie, you grow an extra pair of legs behind your last pair, with a new torso with the length the same as your current lower torso attaching both together. Your tail, butt and privates will extend to behind your new pair of legs, but all other organs are duplicated an additional time. Those newly grown torsoss can each support twice the human weight, and will remain completely naked. Although you can talk and retain your hand dexterity, you will be treated as no different from a normal racing greyhound by everyone else, and attempts to resist this may be treated as lies as well. That is, if you dare anyone to return you to normal, you will not change at all.
For your dare, you will forget this curse until you are sent to a greyhound track, where you perceive this curse aslaid by a staff member there. Somehow. Yes, I know they typically train their greyhounds to be silent, or muzzle them, so this curse essentially loses its effect by then. Whatever. Enjoy your life as a dog taur." The call ended there.
"What is this freak talking about? I've never even lied once in my life!"
Unfortunately, she had, and the curse took effect right there, right then: Jen felt her hindquarters and privates extend backwards while two new legs extend from the growing torso, eventually touching the ground. Turning around, she saw two torsos and two pairs of legs behind her upper torso. If she continues lying this way, she'll only grow more legs, and it will become more and more difficult for her to maneuver herself.
"Jennifer, you're nearly grown-up now, I'll have to send you back to the greyhound tracks", her mother cooed.