A werewolf just like you'd expect from a movie stands next to you. You've seen many excellent costumes tonight, but you find yourself fixated on his. You admire the messy look of his dark grey fur. You watch the subtle twitch of his canine ear. You see the moisture on his nose and his gently wagging tail. His clothes are torn and ragged hanging from his body; they only cover the necessities. How can this possibly be a costume? It's impossibly realistic. He's tall, but not inhumanly so. His muscles stand out, but they look normal for a human who works out. You just can't figure it out, so you ask, "Hey, so... where'd you get that costume?" You look at him expectantly and his imposing yellow eyes meet yours. Suddenly, something of a grin takes his face, and he laughs! What is he laughing at? Yours was a completely reasonable question. After his laughter died down, he responded grinning, "What? Are you looking for one? I just so happen to have a spare,"
"Oh, that'd be great!" You're happy that you might not look so out of place anymore. "Alright, follow me, I've got a secret place to keep 'em so they don't get stolen," You suppose that makes sense, he doesn't have a bag, and they must be quite expensive. He buckles his belt and walks off.
You follow closely behind so as to not lose him in the crowds of costumed people. His pace is quick, and you watch his digitigrade legs carry him, how can human legs fit into those? You follow him away from the crowded zoo streets and down some back alley. The alleys wind until you stop at some wooden box with a lock on it. "Here we are," he begins to pick the lock with his claw, until it clicks open. The werewolf opens the box and in it are several folded werewolf costumes. He pulls one out and hands it to you, "Here you go. Don't bother with underwear, the costume will be under your clothes," You give him a hesitant okay and go around a corner to change.
You strip down fully, and your body shivers in the chill air of the night. Your dick is especially uncomfortable. However, the costume is covered in fur, so you should warm up. Gladly slipping your legs through the slit on the back into its warmth, your feet fall awkwardly into the foot paws. You find them most tolerable when you stand on your toes and the paw pads of the costume. The digitigrade legs still look a bit strange, but that may be fix-able. It is then that you notice the hole in the costume in front of your dick. A hollow extension that looks like a proper wolf's penis is there. You gawk at it momentarily before slipping your member into its admittably greater size. The slick material welcomes your dick slightly pleasurably into it.
A "werewolf" from the waist down, you continue putting it on and place your arms into the sleeves of the costume, and your hands come nicely into the paws. You flex your hand a bit and move it about, seeing the paw act dexterously as your hand commands it. Satsified thus far, you slip the mask over your head, finishing the costume. You postion your eyes to see the costume; you are disappointed. Your legs look awkward, parts of the costume hang loosely on your frame, the tail is limp, the dick is deflated, the muzzle is hollow and sags from your face, and the ears hardly stand. Why does it look so good on the other man and not you? Is there something he forgot to give you? There must be something wrong...
You frown and grope your back for the slit to exit the costume, but you find nothing but fur. Your looking becomes more frantic until you realize that you're stuck in this werewolf costume. You begin to panic before a strange feeling takes your whole body. A dull ache coats you and numbness drops you to the ground. The strange mix of sensations makes you grate your teeth. You feel your body swelling all around. None of the costume is loose as muscles grow beneath the fur. Your bones shift in your legs until they look like real digitigrade legs. Your paws fill out and your pecs and abs grow in. By the end of this, you look like a moderate body builder -- just like the other werewolf. The bone-shifting pain heats up your tailbone until a tail sprouts forth, filling the costume and causing it to wag slowly; your ass tones beneath it. Your bared teeth grow sharp and push forward with your nose and mouth. You fill up the muzzle and your nose becomes wet. You open your eyes to see your new muzzle and dimly register that your eyes have become yellow. Your ears move to the top of your head and join with the costume's canine ears, listening intently to your own panting. Finally, your penis feels pangs of pleasure. Your dick heats up with arousal as it grows into its place. The red rocket gains life and you stare at it, shocked. You calm down after your transformation, and it tucks itself away for now.
Slowly, you stand on your new legs. You look around and notice that you can see the once-dark alley with significant clarity. You round the corner to see the werewolf from before, standing against the wall impatiently. "It's about time, how do you like your new costume? I think it suits you, welcome to the pack," You look at him confused; this is... nice, right? You're pretty sure you like this. You wanted a costume, after all. Now he's mentioned a pack. Yeah, you love being in his pack! You can't wait to meet the rest! "Glad to see you're taking it well. Now that you're in the pack, it's about time we..."