"What seems to be the problem officer?" You ask, smiling coyly at the distressed Woman.
"You were driving erratically, and..." She pauses, trying to collect her thoughts. "... Masturbating." She stares at your cock bulge, her eyes hazy and unfocused. You were planning to fuck your girlfriend into a sexy dog person, but this seems like a good opportunity to take your new body for a test drive. You open your car door, your girlfriend will have to wait. The officer steps back. "Sir! get back in your vehicle." You rise to your full height, your paws grip the ground as you prepare to pounce. She reaches for her gun, but you quickly launch at her, pinning her to the ground with your furry body. You pull her into a kiss, and run your pawed fingers through her hair. She returns the kiss, like her body is on auto pilot. You shred her pants off with your claws and her breathing quickens, almost like she's panting. You grab her hips and flip her over preparing to take her, doggy style.
"Please... no." she whispers, rallying all her will power. Her body refuses to budge, and you plunge into her juicy depths, making her moan. You piston inside her, your brief's waistband stretched under your cock. Her moans get louder and louder until you erupt in her, causing her to howl in pleasure.
You lay with your new lover in the grass, enjoying the afterglow. Getting a better look at her, you notice she has changed a bit. Her teeth look sharper, she has a long tongue hanging from her panting mouth, and her fingernails have begun to resemble claws. It seems like you have the power to change people without the Beast Briefs, just slowly. "Oh yeah, the briefs!" you say, and walk to your car, you return with a new pair. You approach the puppyish girl with a mischievous grin.
She giggles, not understanding what is going on, but enjoying herself anyway. You pick up her legs and feed them into the holes. You slowly pull the band up past her luscious thighs, and her pussy juice immediately soaks through the cotton.
She looks confused, but then the waves of pleasure take over. Her pointed ears poke through her hair, and her mouth and nose pull out into a muzzle. She rips her shirt open, exposing her expanding breasts. Her fingers puff up as she runs her forming paws over her sensitive body. A carpet of brown fur spreads, starting from her vagina. Your dick goes rock hard at the sight of the extra rows of nipples sprouting down her belly. Finally, she whimpers in pain as her shoes stretch to their limit. She gasps as her toes burst free. You help her remove the rest of the restrictive footwear. She stretches her new paws as they finish puffing up.
She stands, shaky on her new legs, but within moments, she is dancing and enjoying her new body. Her dance mesmerizes you, her curvy hips pulling you in as she looks over her shoulder and winks.